There is a big difference between hacking a Coinbase client contact database, and hacking THE Coinbase account database. The thing that might have been hacked

There is a big difference between hacking a Coinbase client contact database, and hacking THE Coinbase account database. The thing that might have been hacked could have easily been a CRM or email marketing system - possibly even via some 3rd party supplier. Obviously there was no hack of the Coinbase accounting system - for the reasons you mentioned.