Since the Turbo Arrow variants can climb well beyond 12500, there must be some sort of cabin pressurization system on board. Obviously this isn't modeled in the sim (why would it be), but wouldn't there at lease be some sort of instrument showing cabin pressure and possibly a circuit breaker for it? I don't seem to see anything of the sort.
The Turbo Arrow is not pressurized in real life. For flight operations above 12500 ft, the pilot and passengers must use supplemental oxygen.
Lots of high flying turbo Pistons dont have pressureization. Hell. The sr22 turbo can get up to 25,000 and no pressure, and it does well at the flight levels. You need an actual mask above 18,000 though, lots of people can't get away with just nasal canulas above 18.
Piper isn't really a high flyer because while turbo it doesn't have a lot of power.