It depends on your coin control. If you merge your faked outputs in the future, then it doesn't help.
I totally agree, people need to know what they are doing, if they start to merge utxos without any coin control, then all the previous mixers and coin-join transaction become useless and a waste of fees.
How is that even possible?
To help understand easily. let's suppose i have my Bitcoin coins in Wallet A, Wallet B and Wallet C and I created a new Wallet Wallet D.
I used mixers to mix my coins from Wallet A to Wallet D. Also i mixed my coins from Wallet B and C into Wallet D.
Now Wallet D contains all my bitcoins with three UTXOs. Now I Consolidating UTXOs to a change address in my wallet. Since i have mixed my coins from three wallets to my new Wallet D, no one can know the source of these transactions. Now Consolidating UTXOs one can only see that these all bitcoin belongs to one person but they will not know that these coins were mixed before reaching the Wallet D.