but it's not like bitcoin transaction can't be reversed. Yes, it can be reversed and it depends on what wallet you use. If you use Electrum and your transaction hasn't got confirmation yet, then you have an option to cancel it by doing a double-spend.
I guess whoever in this thread know that we have feature called RBF in Bitcoin and we can utilize it if transaction does not get any confirmations. More importantly, your wallet should support RBF and it should be enabled before you make the transaction. But the problem is, we are not talking about any wallet here. Yomix is an mixer and they are not like a typical wallet. So there is no option to cancel the transaction or change the transaction once the request is already made. It's an automatic service and as a service, they should not edit any kind of information that user input to their system. This is one of the most sensitive service on the internet.