It also supports my claim that using center channel for vocal is wrong and superficial.
Here we go again.
The use of the centre channel is at the discretion of the mix engineer, and it is not wrong to put a vocal there, but a matter of taste & choice.
You may as well say it is WRONG to split a drumkit.
Or WRONG to mix the bass louder than a guitar.
or WRONG to make the vocal sit back in the mix.