Maybe it's better to turn off the "mining rewards" as an additional feature, at least until they implement it better and obviously, it's not set up well. This is not crucial for a mixer service it only unnecessarily casts doubt on the functionality of the whole mixing service.
As GazetaBitcoin calculated, there is a significant amount that can be "saved" with only 2000 satoshi per user, but why would anyone do it and think in such a way, when the very idea of staking came from the owner of a whirlwind? Just stop this option and continue working on mixing only.
The idea behind the anonymity mining campaign was to build a strong anonymity set and therefore make their main service (mixing) more attractive.
The fact that the implementation is somewhat lacking in user experience for some people doesn't negate the fact that it is indeed helping the anonymity set.
It is simply and incentive to deposit and also hold coins on the site while the campaign is running.
If they stop giving mining rewards, then perhaps the Anonymity set will decrease, as there will be no reason to leave your coins in a central mixer that may run away with your money and you will not get a return through it.
If I am not mistaken then the anonymity set can not decrease. Even if they stop the campaign, there will still be said 567 deposits and that number will not decrease. From that point on, every withdrawal made on the site could originate from one or multiple of the 567 deposits. Stopping the campaign would probably lead to people withdrawing their coins and the anonymity set increasing slower but it could not decrease.