Chain analysis companies have been able to track users of ChipMixer as well as Wasabi. Post-mix behavior is always an important factor for maintaining privacy.
This is correct. ChipMixer is not magic one step button to achieve privacy without any understanding. There are many factors that affect mixing and post-mix behavior is very important.
you can't link deposits with withdrawals
KuCoin investigation shows that hackers (that unfortunately used our service) deposited large and much above average amount of funds into address (later identifed as ChipMixer) and then sweeped same amount of chips next block. They did this multiple times - each time joining sweeped funds with previous sweeped funds. If address A has 123.456 BTC while address B has 0 - then after 100 blocks address A has 0 BTC while address B has 123.456 (minus mining fees) any blockchain analysis will know. This is post-mix behavior that makes you lose privacy.
If you are mixing average amounts - your protection is better. If you wait before sweep or spend - your protection is better. If you do not understand what you do - motivated attacker will break your privacy.
Those are important articles for anyone interested in blockchain privacy. There is lot of money spent to track those big targets. You can read about their mistakes and learn how to avoid them for free.