tbh, though I think they're one of the best
true but that's damning with faint praise. you know Apple is dragging their feet when the most popular eGPU enclosure is a Razer Chroma from PC-LAND. Apple were only promising eGPU type stuff when I bought my 15" MacBook Pro... in 2011! They still don't make one!
Anyway, Thunderbolt is royalty free for a few years now. Apple are a co-developer of it. if Apple wanted Thunderbolt on an AMD Mac, Apple would have Thunderbolt on an AMD Mac.
I think it's clear that Apple are not interested in making an AMD Mac, because their next shift is to in-house CPUs.