To say the RD guides the chain to the front sprocket is a bit of a stretch since it's a foot away. But yes, If the chain is coming off it would be to the outside since that's where the RD lower pulley should be in high gear.

But in normal riding the chain should run from the top of the outer sprocket unguided to the chainring (RD should touch it except during a shift) and stay on. So if the RD pulley is directly below the sprocket the angle should be the same and the chain shouldn't derail. The difference is chain tension and gravity which can overcome a bit of friction in upper (forward turning) engagement, but not lower in borderline cases.