The key point of that link was that Order 227 is that it was directed towards officers, not enlisted men. The other key point was that orderly retreats are allowed, and since you order all retreats in the game (sans Sturm Officier, but there's no way to differentiate that with the game tools) none of the retreats in the game are disorderly retreats.
Justifying a retreat-stopping ability with Order 227 plays much more into the stereotype that no retreats were allowed. I'm not disagreeing that an FRP on commissar would be nice, but leave 227 out of the justification.
That's not even completely true. It was partially directed at officers, but who do you think was doing the retreating? The soldiers. So, using a commissar to halt a retreat all the way back to base does in fact fit with the spirit of Not One Step Back. Which, again, nobody had implied that the commissar would be shooting the troops, just that they would halt them from retreating further. And that, again, fits wholly within the verbage of the order.