You should be concerned of an active Sybil attacker regardless of whether other inputs are rejected or not. Mining fees prevent continuous attacks, large sized rounds prevent single attacks.
Maybe you should be concerned a little more if you're voluntarily giving the power to a chain analysis company to decide to execute the Sybil attack more trivially?
If rejections were arbitrary and commonplace then that would give you an eager customer base from which you could attract users to your own WabiSabi coinjoin coordinator. Why haven't you set up your own WabiSabi coinjoin coordinator yet?
Here you are, engaging in whataboutism for the billionth time. This isn't what Pmalek asked you. It's pretty simple to grasp, but apparently not as simple to ignore it: the company responsible for Wasabi is preaching about openness and transparency. Why would it let a chain analysis company, which is described by the lack of both openness and transparency, decide who isn't allowed to coinjoin?