bleeding brakes

I'm OK with your being against it. I think you're over-thinking this, it's been working just fine for me for about a decade, but I'm not going to force anyone to use this method. I recently noticed that rust let the epoxy loose, so a new peanut butter jar is needed.

Even with assembly lube in the bleeder threads it still will pull air past them if there is a serious problem upstream somewhere.
FWIW there is no such thing as "negative pressure". There is only pressure and the absence or partial absence of it. So the all-out absolute most lack of pressure that can be applied to the system is zero psi, down from the atmospheric 14.7 psi. Not like we can get a couple hundred psi on this thing. Assuming that the average car idles at 15" of Mercury that translates into being 7.4 psi. Not a lot of pressure possible.

Is pulling air past the wheel cylinder cups so horrible? My time in designing racing disc brake stuff never exposed me to drums.

FWIW I didn't use this method on my Valiant after putting new SS hoses on it and assembling the AR brackets with wilwood DynaPro's on the OE rotors. The engine wasn't running then and the system gravity bled almost perfectly.