The reason to sous vide (in butter, which is really more like 'butter poaching' than straight ahead sous vide) is to use a low temp and short time and arrive at a cooked, but softer, creamier texture than a trad boil/broil/steam
if what I wanted was a typically boiled lobster texture, I'd typically boil it
the one minute par boil just makes it easier to remove form the shell. it has no discernible effect on texture; and it's certainly not "cooked" that fast.
If I want a more traditional texture, my favorite is to par boil for a few minutes, split down the middle, lie it on its back on a sheet pan, butter liberally, maybe bread crumbs in the cavity, and then under the broiler to finish... the way many "steakhouses" do them.
SO MUCH better than (yawn) steamed.