I see your point of view and you are right, I totally agree. But your answer has nothing to do with the original question.
I asked that why do we need bitcoin mixers, if there is Monero. We can change BTC to XMR and vica versa on no-KYC exchanges, and make an XMR to XMR transaction between the changes. This is a theoretical question.
if just using 1 exchange there is no point using xmr at all, just use the exchanges own algo internally to ensure deposits are different to withdrawals (aka unadvertised mixing, by branding themselves as an exchange instead)
yes XMR can be used as the middle path to make sure deposited btc in exchange1 is not the same as withdrawn btc in exchange2 due to different btc reserves..
but that would require you using 2 exchanges to guarantee different reserves of btc for it to need XMR to traverse the 2 exchanges
XMR is by regulation standard a AEC (anonymity enhanced currency) which also flags up as suspicious if found users are converting btc to xmr.
so investigators do try to watch XMR too
so finding a service that does it without KYC becomes difficult because most advertised exchanges have to register as money service businesses and then comply to regulations..
any MSB not complying to regulations by not registering usually gets caught