You shouldn't be using an exchange as a mixer, I don't know how many times I have to repeat that this month. Exchanges aren't businesses with main scope to make your coins untraceable. Pretty much the opposite. They very much keep track of what's going on, and most are likely to share it with chain analysis companies. There is even a site that lets you search to which exchange an address belongs to:
https://www.walletexplorer.com/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.