Various regulatory bodies are fighting over crypto as they want to be the one to regulate it. Coinbase is just stuck in the middle of the battle for control.
Gary Gensler and Rostin Behnam consider Bitcoin a commodity in the crypto space, so would be regulated by the CFTC.
Every other crypto (probably even Ethereum) is a security, and so falls under the SEC's jurisdiction.
That's what they've been signalling for a while now.