20 year old house and the toilet had been rocking. After a use,
noticed water leaking from ceiling below. Went to pull the toilet and
screws corroded and pulled right out.

Replacing the toilet today. Reviewed wax ring and toilet installation.

Is there a true need to pull out drywall from ceiling below to analize
leak damage? From the look of the screws, it has been going on for a
while.

Or, just replace toilet, patch water damage and move on?