head milling

Ok sorry to bring up a dead horse here but I binge watched "318wullrun"'s you tube videos last night pertaining to the top end rebuild on his 77 van.
This is something I have been curious about for a while.
Now usually when I take a set of heads in for machine shop service they reface them while they have them just to make sure they ain't warped. Usually when I ask them how much they took off it's less than 10 thou.
I read all the time about having to also take off the intake side when you mill the deck surface.
Considering that most commonly used aftermarket head gaskets are thicker than the original, can't you take that difference off tye deck surface and not touch the intake manifold face?
If the original shim style ones were 0.020 and the replacements are 0.040 that means you should be able to take at least the difference off the deck surface without touching the intake side. Right? And would definitely want to as well.