Entities are no longer resaved when added to a group. Their cache tags are invalidated instead.

In earlier versions of Group, adding an entity to a group would trigger that entity to be saved. This could lead to a new entity being saved twice and often caused trouble.

From version 4 onward, the entity will no longer be saved, but its cache tags will be cleared instead. Any cached information based on said entity will therefore be invalidated and can be calculated anew with Group's access rules being applied.

Please note that this impacts modules which create entities or database records based on the creation of third-party entities, such as Pathauto creating or updating aliases for entities being saved. It is up to these modules to use hook_ENTITY_TYPE_insert() for group_relationship and call ::getEntity() on the newly created GroupRelationship entity to get the entity that was just added to a group.