Besides the fact that these types of speculations have no productive outcome, I personally believe this is too far fetched.
After all, ChipMixer has been one of the longest-standing mixers out there, mixing a ton of BTC, meanwhile others have come and gone. Even to the point where a few months ago people started speculating whether CM was a honeypot.

To me, it looks like the ChipMixer operators have run it quite competently, with the one mistake (if actually true) to store 7 actual TB of data. What makes or breaks a privacy service (for me) is that they collect and store as little data as possible.
In a business context, 7TB is nothing. That's what people have in their personal home NAS systems. But for a privacy service, I don't know what kind of big files you really need to permanently store.