HP gain with multi angle valve/seat

I read that a multi angle added 25 hp by adding more CFM. I having a hard time with that many cfm produced by multi angles
I think it's probably true with the accompanying bowl work that most "sane" people would have done at the same time, and especially with full port work. I don't think most people would do "just" a multi angle valve job and "nothing else". That doesn't sound logical, does it?