What do you mean "combining UTXOs outside of a Wasabi coinjoin", lol?
If a user funds their Samourai wallet, then Samourai creates a Tx0 to segregated unmixed change. If the user chooses to then combine a coinjoin output with that unmixed change, then there is nothing the coinjoin protocol can do to stop them.
If a user funds their Wasabi wallet, the transaction which funds that wallet will create unmixed change. If the user chooses to then combine a (surveilled and permissioned) coinjoin output with that unmixed change, then there is nothing the coinjoin protocol can do to stop them.
There is no unmixed change in WabiSabi coinjoins unless you are the whale, look at this transaction and see for yourself - ALL outputs gained privacy since they cannot be matched to any input:
https://mempool.space/tx/633128233af9c571e8fb99a28b10c195a102da7081a027e0cf657cdce9573909If a user swaps some coins to monero, the transaction which funded that swap will create unmixed change. If the user then swaps some monero back to bitcoin and combines that new bitcoin with the unmixed change, then there is nothing monero can do to stop them.
Every privacy service or protocol in existence has the same weakness of a user combining unmixed changed with mixed outputs. That is not the fault of the privacy service or protocol, but the fault of the user.
It was a fault of every privacy protocol until the WabiSabi protocol fixed it. Only whales can receive unmixed change, and that unmixed change just gets automatically remixed until it's entirely mixed.
On the other hand, the flaws in Wasabi such as constant address reuse
Can you explain to me why you aren't warning these people you are recommending Samourai's Whirlpool to about their constant address reuse?
Exposing someone for using sock puppets isn't "doxxing".