No, GC does not specifically meet that GM spec. Syntec 5w30 & 10w30 are the only Syntec grades that carry the GM 6094M spec.
It's probably because GC is geared toward the European crowd. Read the label on the back of the GC bottle & you'll see what I mean.
I'm sure GC would pass the GM 6094M spec, but since no American cars (that I'm aware of) call for 0wXX oils, Castrol probably figured "Why bother with the GM spec?"
6094M is for 10w-30 only I think. It's not a tought spec at all, EVERY single SL/GF-3 oil met it. It requires no more than like 50,000 Cp at -30C for cold pumping. Most GF-4 10w-30s are well below 20,000. I think it just makes it so Joe Bob doesn't fill his crankcase with 1980 10w-30, which would be near the pumping and cranking limits allowed by the API.