Deletion of Files on Custom FIelds doesn't delete file if entity is deleted.
Tested on master and 5.48
Create a custom field for a file on a contact - or activity (haven't tested elsewhere) Create a new entity with a file on that contact. Identify uploaded file name in civicrm_file Find location of the file on the server. Copy the url to download the file.
Delete the entity - then Delete from Trash. See notification about all related data being deleted. Check the civicrm_file table. Row is still present.
Check the file on the file system - file is still present. Attempt to download the file - it will still download.
Deleting the file via the edit custom field click the trash item does delete the file. Deleting an activity with an attachment does work.
It looks like rows are not removed from civcirm_entity_file either. However it looks like perhaps they are not added when the custom field is on an individual?
I think it's reasonable for a user to consider that deleting an Activity Attachment and deleting a file attached via a custom field should function the same way.
Additionally by not deleting these files you run into issues with GDPR.