This game has very little to do with real life (for example, most of the best perimeter defenders in the NBA are long, fairly tall wing players, yet the training bonus for OD goes to shorter players) so I usually don't engage in these debates but you're just straight up wrong about Magic being the only NBA point guard to ever be 6'7" or taller. Sun Yue who was in the NBA last year is 6'9", Shaun Livingston is 6'7", Penny Hardaway was 6'7" and played a lot of point guard, Scotty Pippen was a wing player but regularly ran the point in the triangle offense when he was with the Bulls (particularly late in games when they needed Kerr on the floor to spread things out for MJ), I think Marko Jaric might be 6'7, too. These are just guys off the top of my head and I am sure there are a ton more.
People also need to stop trying to conceive of things purely in terms of the NBA. Almost every division in this game is not meant to represent the top flight leagues like the NBA or the ACB. USA V is essentially one of the many amateur circuits in the US, IV is the IBL/ABA/EBA and other semi-pro exposure leagues, USA III is probably best thought of as the PBL, and II as the d-league. In the lower minor leagues there are a ton of guys playing positions that their height would suggest they shouldn't be playing (6'5" centres are super common in leagues like the ABA).
All of that is to say: you're wrong about NBA point guards and height, and you're wrong to try to draw so many comparisons to the NBA.