So, I am trying to synchronize files to Amazon S3 using the s3_sync module. The playbook works properly, with the exception of the file_change_strategy parameter date_size. It seems to ignore files with same size, but different (more recent) dates. Here is my playbook:
So, after posting this question, I found a bug report on the same issue: https://github.com/ansible/ansible/issues/54076
Posting this answer for others.