If I learn anything from Chipmixer or how mixing companies store their customer's data while they claim the opposite, it is unwise to assume nothing can go wrong at all.
Unless you're somewhat informed beforehand, we don't yet know what information was ChipMixer keeping in their hard drives. It could be anything, from 4k movies to several blockchain full nodes.
So, it's just false to argue they were keeping customer's data.
That's confirmation bias at its finest, to put it lightly.
You assume the worst for business A, all while assuming the best for business B. No business is a saint, that's the cold harsh truth.