Phone field storing a default even when left blank

[Kurt]

I have a custom entity with a Phone field that is optional. During creation of that entity, if I leave the phone field blank it seems to be defaulting to the phone value that is set on the user creating the entity.

If I later go in and edit the phone field I can set it to blank without a problem, so this is specific to the entity creation path.

The same behavior seems to happen for an optional email field -- if left blank it takes the value from the user's email.

How can I suppress this behavior? I want to be able to leave those optional fields blank.

[Kurt]

Also worth noting I'm fine with editing core code to get this done.