Not sure I understand your intent here, as that seems to make no sense at all to me. Why would you want the channel fader linked to the gain control?
Just like he wrote; to make up for using the "pre-gain" for gainstaging. So if he has an EQ in an insert and it's clipping then lowering the "pre-gain" would solve that, and if the fader was inversely proportional it would make up for that loss.
I wouldn't do that, but that's what it looks like to me.
You should set your trim level to recorded level before you do any mixing...not subjective...granted, I suppose you could debate WHAT exact value in the digital world you want to calibrate it to...but, you don't CHANGE it once the mix is underway. What would be the purpose?
You're not going to clip a software EQ with the input trim set correctly. You might boost a lot with the EQ and need to turn the FADER down (although I wouldn't use an EQ without gain makeup stage)...but, there's never a scenario I can think of where you would properly need to change the trim once a mix is started.