"Sync from" and "Sync to" cannot be the same scheme.

Installed, enabled and in settings.php I have:

$schemes['s3'] = [
  'driver' => 's3',
  'config' => [
    'key'    => 'MYKEY',
    'secret' => MYSECRETKEY',
    'region' => 'eu-west-3',
    'bucket' => 'bucket-name',
  ],

  'cache' => TRUE, // Creates a metadata cache to speed up lookups.
];

# dont't forget this line
$settings['flysystem'] = $schemes;

I can now see "Flysystem: s3" under "Default download method" but when I go to the tab "Flysystem" and I try to select s3 (only option on both), I get an error saying "Sync from" and "Sync to" cannot be the same scheme."
I am lost. What I am doing wrong?