Coinbase made everyone whole, and the attackers stole the credentials (not because of Coinbase's fault) ahead of time, and the attackers had to perform a "SIM swap" type attack on the users. "Breach" may be the required term for the Californian government, but this wouldn't qualify to most people as a traditional breach (i.e., compromise of Coinbase's infrastructure). Edit: California, not Canada. My bad.
6000 customers affected. If it wasn't a YC company you'd never say that.