Maybe I’m off here, but this doesn’t really seem like it’s about the 30% commission. Maybe Apple is taking a position against allowing crypto trades on their platform?
AFAIK paying for 'gas' is paying for a digital service of computation. This is covered by Apple's App Store Guidelines https://developer.apple.com/app-store/review/guidelines/#bus... for years and years.
Being a consumer who buys digital services through an app hosted by App Store should have some recourse. And that's, again AFAIK, what Apple does with its Guidelines...help empower the consumer should, theoretically, Coinbase not uphold their part of the digital purchase fulfillment relationship when $$ was exchanged on an iPhone app.
Apple didn't block fungible tokens (crypto), they only blocked non-fungible tokens (NFTs). Right now is the time for them to clarify their position.