A13 Bionic uses ARMv8.3-A. Qualcomm 865 (which is newer than A13) uses ARMv8.2-A.
My guess is they influenced the spec to add feature deltas from v8.2->8.3 into the spec. Sure, it's not non-standard, but it seems like most vendors pick and choose what instructions to implement from each ARM spec.
What that means is the compiler for each processor needs to effectively be specific to that processor. If it's not, you might not be totally optimized.
Anyway, this is no different from targeting x86_64 - you can compile targeting the most recent ISA, or you can run on more hardware. No one says AVX2 is a proprietary extension, but it sure as heck won't work on an older x86_64 cpu.
The original comment's point is this would be good for the RPi org... which use comparatively ancient ARM processors (even the brand new RPi4). I don't see how Apple entering the ARM space on desktop is relevant at all.
