Honestly no reason the majority of this wouldn't apply to "non Apple" arm64. It's sort of like being worried about AMD x86 vs Intel x86. It mostly doesn't matter, except in some cases where it does, but you don't set out to say "I don't want to learn Intel x86, only AMD x86"
You learn arm64, then you can worry about if you need to deal with implementation specific ISA quirks.
You learn arm64, then you can worry about if you need to deal with implementation specific ISA quirks.