Hi Anthony, I think those are interesting points, but there's nothing in it to prove your logic.
And posts that make design claims but have no data make designers look like we're just making stuff up.
I agree with your assertions as being valid, but I don't think "when you only mark optional fields, the form looks cleaner with fewer elements and less cognitive processing." is the full story. Does it produce more errors? SInce it's not what users are used to, are they frustrated by the change?
If you want to keep this up, TEST it!
e.g. test which design:
- produces fewer validation errors
- is completed faster
- has lower frustration levels after completing the form
Share that data and then make your claim.