The combination of content moderation, translations and cancelling user accounts is broken.

I can confirm there are some weird results when cancelling a user account. The node revision list before and after reassigning an account:

mysql> select * from node_field_revision;
+-----+-----+----------+--------+-----+-------+------------+------------+---------+--------+------------------+-------------------------------+----------------------------+------------------------------+
| nid | vid | langcode | status | uid | title | created    | changed    | promote | sticky | default_langcode | revision_translation_affected | content_translation_source | content_translation_outdated |
+-----+-----+----------+--------+-----+-------+------------+------------+---------+--------+------------------+-------------------------------+----------------------------+------------------------------+
|   1 |   1 | en       |      0 |   2 | Test  | 1565335142 | 1565335149 |       1 |      0 |                1 |                             1 | und                        |                            0 |
|   1 |   2 | en       |      1 |   2 | Test  | 1565335142 | 1565335191 |       1 |      0 |                1 |                             1 | und                        |                            0 |
|   1 |   3 | en       |      1 |   2 | Test  | 1565335142 | 1565335197 |       1 |      0 |                1 |                             1 | und                        |                            0 |
|   1 |   4 | ca       |      0 |   2 | Test  | 1565335201 | 1565335207 |       1 |      0 |                0 |                             1 | en                         |                            0 |
|   1 |   4 | en       |      1 |   2 | Test  | 1565335142 | 1565335197 |       1 |      0 |                1 |                          NULL | und                        |                            0 |
+-----+-----+----------+--------+-----+-------+------------+------------+---------+--------+------------------+-------------------------------+----------------------------+------------------------------+
5 rows in set (0.00 sec)

mysql> mysql> select * from node_field_revision;
+-----+-----+----------+--------+-----+----------+------------+------------+---------+--------+------------------+-------------------------------+----------------------------+------------------------------+
| nid | vid | langcode | status | uid | title    | created    | changed    | promote | sticky | default_langcode | revision_translation_affected | content_translation_source | content_translation_outdated |
+-----+-----+----------+--------+-----+----------+------------+------------+---------+--------+------------------+-------------------------------+----------------------------+------------------------------+
|   1 |   6 | en       |      0 |   0 | Test     | 1565335142 | 1565335632 |       1 |      0 |                1 |                             1 | und                        |                            0 |
|   1 |   7 | en       |      1 |   0 | Test     | 1565335142 | 1565335632 |       1 |      0 |                1 |                             1 | und                        |                            0 |
|   1 |   8 | en       |      1 |   0 | Test     | 1565335142 | 1565335632 |       1 |      0 |                1 |                             1 | und                        |                            0 |
|   1 |   9 | ca       |      0 |   0 | Test     | 1565335201 | 1565335632 |       1 |      0 |                0 |                             1 | en                         |                            0 |
|   1 |   9 | en       |      1 |   0 | Test     | 1565335142 | 1565335632 |       1 |      0 |                1 |                             1 | und                        |                            0 |
|   1 |  10 | ca       |      0 |   0 | Test     | 1565335201 | 1565335632 |       1 |      0 |                0 |                             1 | en                         |                            0 |
|   1 |  10 | en       |      1 |   0 | Test     | 1565335142 | 1565335632 |       1 |      0 |                1 |                             1 | und                        |                            0 |
|   1 |  11 | ca       |      0 |   0 | Test123  | 1565335201 | 1565335632 |       1 |      0 |                0 |                             1 | en                         |                            0 |
|   1 |  11 | en       |      1 |   0 | Test     | 1565335142 | 1565335632 |       1 |      0 |                1 |                             1 | und                        |                            0 |
|   1 |  12 | ca       |      0 |   0 | Test123  | 1565335201 | 1565335632 |       1 |      0 |                0 |                             1 | en                         |                            0 |
|   1 |  12 | en       |      1 |   0 | Test     | 1565335142 | 1565335632 |       1 |      0 |                1 |                             1 | und                        |                            0 |
+-----+-----+----------+--------+-----+----------+------------+------------+---------+--------+------------------+-------------------------------+----------------------------+------------------------------+
11 rows in set (0.00 sec)

A lot of additional revisions are created when reassigning each revision. revision_translation_affected seems to get reassigned to '1' for all revisions as well.

I believe this is primarily because when each revision is updated, content moderation forces a new revision to be created. There might be other bugs that come into play during the update, but I think that explains the large number of extra revisions after cancelling the account.