A lot of the times, when you see “does not fit with....” it really comes down to the fact that they may not have tried that combination of parts, so to cover their butts, they say that. Sometimes they have tried to parts and they just flat won’t work with each other.
As for you question about chiseled low bars, I can’t really think of a reason wiring heated grips wouldn’t work. You’re already going to be internally wiring them for your switches and throttle, so what’s a few extra wires going to matter.
2018 FLTRXS Wicked Red
Harley Master Tech
Disabled Combat Vet - JTAC 96-06