When he took his 3rd it was 2 tech labbed facts and 3 reactored. His Hellion harass was exemplary and he nailed about 40 probes before he ever pushed out.
Honestly, if you're killing that many probes, you can probably win with whatever you want.
The other thing with 'meching' against protoss, I think, is that you need air units (banshees/vikings) and ghosts to beat gateway/robo armies (archons/immortals/colo/chargelots) which means protoss gets fast 3/3 with chrono, and you never really get 3/3 on all your units regardless (unless you can afford 4 armories or something dumb).
3/3/3 protoss units are -good- against 2/2 or so mech.
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