I don`t play Metal, but I can tell you that for many years the Master/Pull was most strange to me compared to the others. Pulled, was first too bold for me, and pushed in, too thin.
Nevertheless I`ve got used to the pulled function and never push in, as this state is unusable for me.
Definitively I`ve got the confirmation from a tech after he took a look inside the schems and told me that the all "Pulled"-functions are nothing else but the "Normal"-function as i.ex on old Fender amps.
"Pushed in", some frequences are filtered out. Nothing more.
Doing this, for me the sound is just worsening, nothing more.
Of course strat-sounds will be fattened when pulled, but humbuckers sound FAR too thin when pushed in.
I`m playing two Les Pauls with Gary Moore Burstbuckers No. 3 in bridge position.
What MESA tells in the owner`s manual about this function is nothing but bull****, but there are in deed people who like to use the "pushed in" function, maybe for their very own spacial Music.
And if you don`t like both functions, they can be modified, the "Pulled" can be lowered, and the "Pushed in" can be fattened by altering some electronic parts.