Right, my wife has "piano-only" perfect pitch -- she'll recognize the key played on a piano, but if you sing a pitch (or play it on any other instrument) her accuracy goes down -- it's just based on years and years of playing piano. She can kind of hack singing a pitch (for example) by imagining playing the note on a piano, then trying to sing the pitch in her head.

I doubt she'd notice if a piano was tuned to 442 vs. 440, though... which makes some sense, really; a violinist really benefits from a sharp ear for pitch, for accurate finger placement (no frets or anything like that on a violin neck) -- but a pianist has a fixed set of keys to choose from.

That's interesting. My closest hack to fake perfect pitch is to estimate the range of a note my humming it or singing it. It works because my vocal range is more or less absolute, and I can easily feel how difficult the pitch is to sing by trying an octave above or below it.