When getting transitions from rest API, not all required fields are marked as "required"?

I did set in the test workflow 2 validators for reopened transition:

  1. The assignee field has to be set.
  2. Resolution field has to be modified.
    There is also a screen assigned to that transition that has both the required fields and few additional. When manually doing the transition, both of the required fields need to be set.
    I’m using the get transitions to get all transitions’ information. After a call:

I’m getting all the transitions’ data from Jira, however in the reopened transition, field assignee is not marked as required. Only the resolution field is marked as required.
I’m testing it with an issue that has no assignee assigned yet, so I’m surprised with this behaviour.
Is this expected an behaviour?
Is there some more documentation about it (except https://developer.atlassian.com/cloud/jira/platform/rest/v3/api-group-issues/#api-rest-api-3-issue-issueidorkey-transitions-get that I could check?