I don't really think that's the reason it works. It works better because the center and the playside guard will block down harder, allowing the pulling guard to get around easier. When I run the Power O and it fails, it's normally because someone came through the A gap. On a play where the LG is pulling to the right, the C has to pick up the guy over him, and that leaves any one coming in the other a-gap for the RG. On the Power play, the RT then has to take the B-gap over where the RG used to be, allowing the pulling guard and FB to lead the way. On a trap play, the RT wouldn't move, and the pulling LG and FB would move up the gap the RG used to occupy.
The problem in Madden a lot, is that the C and playside guards don't always do a very good job of blocking down on those A-gaps. That's why you see these Qb's getting tackled before a handoff, which you never see in real football (why that was an achievement, I do not understand). So sliding away from the play gets the C, playside G and T to take a better first step like they're supposed to.
On of the problems I've always had with EA's sports games blocking is that they seem to rely too much on zone blocking. There really isn't a whole lot of man blocking. The Power O play has some okay man blocking, but the OL logic for man blocking schemes needs to be improves. The OL in madden almost always has a spot to block, and not a guy they're supposed to block. And you never see things like double teaming up to the next level. The OL/DL interaction would improve a ton, imo, if they added/improved true man blocking run plays, such as powers, traps, leads, etc.