I don't think there's an easy answer to your question. Just because someone's been "doing 10K with M1 since the beginning of time", it doesn't really mean much to you; different driving habits, different oil (M1 formulations have hardly remained the same for 30 years) and a different vehicle.
For me, the big variable is your car's motor. I had no problem going to 10K with a GIII synthetic, but I've seen a TON of UOA's on my particular engine (and the whole Duratec V6 family of engines) to support that decision. I don't know much about the Tau V8 though, and I doubt anyone else on here does, either. I haven't seen a single UOA on it.
Personally, in absence of any other information, I'd keep it to the mfg recommendation of 7.5K, and do a couple of UOA's to see if extending the inteval makes sense. M1 0W20 is certainly capable of doing 10K or more in the right circumstances, but it's only one of the variables in play here.