...and as such, I believe discredits the theory the FBI was able to hack the hacking group.
I see, that makes sense. So if we rule out the possibilities that an exchange just handed FBI their key; and that the FBI hacked the hackers; and (of course) that FBI cracked bitcoin with quantum computers... what are the odds?

Could it be possible that the FBI somehow scammed the hacker with their mixer, and only then applied for a warrant to move the coins further?
..I'm also surprised that the hackers didn't even bother to try something like CoinJoin first.
Mixing 60 BTC+ via CJ is not trivial with today's prices.
I had thought about the possibility that the FBI scammed the hackers via some promise that was unrelated to being a mixer. I am not familiar with the communities the hackers may be a part of. The FBI may have had a CI, or may have had an agent undercover himself in one of these communities, but I would think seizing the coin would blow the cover of either the CI or undercover agent.