> Apple...completely boycotting Google's formats
This is not exactly true, they are a "founding member" of AOM: https://aomedia.org/membership/members/
> Apple's stance is especially interesting because it's unclear to me what they gain by pushing license fee encumbered formats.
My guess is cheaper hardware. AV1 is simply behind HEVC in terms of hardware (ie, ASIC encoder/decoders) support.