Does photoshop retain the metadata of deleted assets?

I've been having issues with the amount of file size inflation Metadata is adding to my PSD's.

A little context, I work with large artwork files, If I open up a large PSD and delete everything including the history, leaving just a solid colour and save it again the file can still be upwards of 100MB.

Ive been given a custom script to run that will strip that down to a few kb but that leads me to my question.

Am I right in assuming that Photoshop is retaining the metadata of deleted assets and if so simply, why?

If there is no benefit to retaining this information would it not seem more logical to remove all associated data with the removed asset?

I have GB of previous files that I now realise could be taking up a fraction of the space they currently are and will eventually need to assumably either just delete them or open them and run a script.