Climbing

I was belaying the other day with a BD GridLock Carabiner (see PDF if you're unfamiliar - it's labelled 'D') and a GriGri.

Had an issue that the GriGri worked its way around the carabiner and was pushing against the gate, essentially trying to open it. Now, obviously I did my pre-climbing checks and so the gate was screwed shut, but I was a little concerned anyway. So, I checked out the manual for the GridLock (see PDF) and it says you're meant to put a GriGri the other way around than when using an ATC. So, firstly, just FYI - this is the way Black Diamond say to do it, with the GriGri in the narrow end of the carabiner (that's the 'crotch' rather than the 'basket').

Okay, so far so good. But then I noticed that the same image suggests that you put the GridLock so that the gate is on the same side as the dead rope (right when belaying if you're right handed). I've always done it the other way around, so I was now additionally confused.

But wait! It gets weirder! Black Diamond's manual also suggests that with a standard screwgate biner, the gate should also be on the dead rope side. Now, this can't possibly be right, surely? Because the rope could potentially roll the gate open.

Now I'm baffled. I've always had the screwgate on the left, away from the rope, because it seems natural to do it that way, and having the screwgate on the right (rope side) seems potentially dangerous, but apparently that's how BD, at least, think it should be done! I'd kinda like an answer to this, given that I'm trusting my climbing buddies' lives to these things.

What are /c/climbing's thoughts on this?