I believe it is as you say. I have no direct evidence, but circumstantially They have never shown 1% of the concern They would have had if crypto--as understood--posed any threat to Their death grip on power through control of money.

But They (specifically through the NSA) were the ones that first released it, right? Reasoning backwards, I believe They must have either known about a flaw or developed a backdoor significant enough to render all crypto harmless if need be (or confiscate or deactivate it at will or whatever).

Being aware of the exact nature of the flaw, They can simply monitor the space to see if anyone seems to be sniffing around at the flaw, or working on developing something that would close off their backdoor. If deemed serious enough, they are made to go away.

Since the plan is ultimately to control tens of trillions of dollars worth of global currency, virtually any amount of resources could be justified towards this project. And They certainly have no rules about "tragic accidents" that may or may not occur.