Indeed. And the limit sounds like not just silicon lottery, but possibly also hard voltage limit, but maybe the breaks come off for the Pi500.
3.14GHz being the last truly stable frequency seems almost deliberate
Right, it does come full circle by half.
It's slightly arbitrary, though; the real limit right now is the voltage limit set in firmware of 1.0000V. I think we could get a stable overclock to at least 3.2 or 3.3 GHz with more voltage.
IIRC it wasn't truly stable, just stable enough to sometimes finish a Geekbench run before crashing.
it can be done higher if voltage is added further. Maybe with certain temp control can achieve 4GHz or more