Citation needed on this one I'm afraid. If nothing else, a currency that the Party cannot control would be A Problem. China did not have much economic benefit in halting the ANT IPO, yet it did not go through all the same. There _might_ be a benefit in allowing bitcoin to continue to exist of course, if they think it advances their cause more than it hurts it. But as soon as that calculus changes, it seems quite likely that the big mining corps (with as you say at the moment of speaking about 65% of total hash rate) will receive some "friendly invitations" (from unfriendly people with guns) to stop their business operations.