It's you lie, I don't reject that we first have written unlimited amount of BTC because 20 BTC to mix is close to unlimited... I'm not sure people mix more per single mix
It sounds like you don't understand the market you are in.
Here's a ChipMixer deposit of 1,000 BTC I am aware of simply because we were discussing it an another thread:
https://mempool.space/tx/1e7c498469369e90dfdd0c8258c6aa5325661553f441a2c6897d93b210f8ef67. There are plenty more such examples.
Further, a balance of 20 BTC does not let you mix anywhere close to 20 BTC. Since we know now that you supposedly have a balance of 20 BTC, if someone were to deposit say 5 BTC to your mixer, then there is a significant chance that their withdrawal would be easily linked to their deposit due simply to matching the size of the inputs and outputs.