There's no such confusion when it comes to the other professions listed, no huge gray area where everyone calls you a physician even though you only work with animals: those are veterinarians.
2 of 68 in my graduating class of BSE students took the PE exam. I think almost all of us now have business cards which include the word 'engineer'. That's not a gopd position from which some outsiders can selectively declare that the term is protected.
My experience has been that anyone who claims 'engineer' is protected is selling something, or at least trying to protect the value of the scheme they bought into. There are a couple jobs that legitimately need it where the regulatory environment requires, but they know who they are and know they are rare.