@Kazibácsi while that may be true, the vast majority of people who say Pinchas would subscribe to the grammarians who would say it's incorrect.. so not so relevant that there exists such a pronunciation. If anything it's being inconsistent.

@robev Moses was given an oral tradition on Mount Sinai and not a grammar book. So who says that the grammarians are always right? Do you always follow Hanau or Satanow? There are many (seemingly) quirks in the Tanakh, which are said in a (seemingly) illogical way, but still the Masoretes recorded that tradition, so we go after that – full stop.