I often here about why they're toted to as having the barrels aligned to be hitting the same hole at a set amount of distance, such as 50 metres. Why?
To me, it'd make more sense to just have them parallel. It'd be easier to manufacture (I think) that way, and about 3/4" of an inch won't make that much of a difference (especially on big game). I mean, if you think about it, a deer's vitals are about 6 MOA (so being 3/4" of isn't a big deal), and I'd assume African big game is a significant amount larger.
And on shotguns, I've always heard you have to aim an inch to the side when shooting clays with a SxS, but not with a pump, semi, or O/U. Considering you're shooting many little pellets, possible making a shot pattern a couple feet wide, I don't think it matters much, no?