Think, if they say that chipmixer holds 7TB, it will cause panic in people and the society will massively say that we shouldn't trust bitcoin mixers because they hold our data. This can damage bitcoin mixing business and make it hard for mixers to gain trust and operate.
Panic without evidence is foolhardy. Concern is a legitimate response, but no one should be resorting to panic when there has been no confirmation on what the 7TB consists of. It could be copies of the blockchain, or even personal files, media or backups belonging to the owner which are totally unrelated to the mixer. For all we know, it could be a bunch of movies they pirated. It could be anything.