They don't have to claim it. Purely by controlling the addresses that held BTC at the time of the fork, Coinbase controls the BCH that magicked into existence.
The issue is that BCH belongs to the original owner of the BTC it was forked from. Despite Coinbase telling people to withdraw their BTC if they wanted the BCH a lot of people no-doubt now feel aggrieved that they're unable to access the new theoretical windfall.
How is that not bullshit though? Like, if I were a company that didn't want to take a side, had projects in the pipeline, and didn't want to have to build out infrastructure, extra warnings, and educational content for the speculators that will probably send BCH <-> XBT, I don't see why I can't tell all the BCH enthusiasts that my company won't redeem the BCH, and to send their funds out so that they can redeem the BCH they're entitled to.
It costs a lot of man hours to add infrastructure work for that, and they're setting a precedent that they'll support every single fork that people speculate with.
I personally think this is lazyman bullshit where people harp about how Coinbase being amicable with the feds are bad until they want to file suit lol. People who were knowledgeable enough about the fork but too lazy to learn how to move their Bitcoin out, not have their private keys stolen/lost, and redeem the coins on two chains without fucking up feel entitled to free money that costs Coinbase man hours and technical debt. Despite all ideals about them technically controlling the BCH, they should be able to draft a legal document placing their licensing at stake that asserts they're not claiming customer BCH and get back to answering my limit increase email.
*Disclaimer: I don't work for Coinbase or a Bitcoin company
The issue is that BCH belongs to the original owner of the BTC it was forked from. Despite Coinbase telling people to withdraw their BTC if they wanted the BCH a lot of people no-doubt now feel aggrieved that they're unable to access the new theoretical windfall.