Bitcoin Magazine Coinbase CEO Brian Armstrong Addresses “Paper Bitcoin” Claims, Claims Bitcoin ETFs Are Fully Backed Coinbase CEO Brian Armstrong dismissed “paper Bitcoin” claims, insisting spot Bitcoin ETFs are fully backed, while defending Coinbase's dominant custody role and calling U.S. regulatory clarity the next key step for the industry. Coinbase CEO Brian Armstrong Addresses “Paper Bitcoin” Claims, Claims Bitcoin ETFs Are Fully Backed Micah Zimmerman.