User blog comment:TheKnightOfOyashiro/PS3 Battlefield 3 patch/@comment-3349991-20111130203736/@comment-28584497-20111202232451

Personal Defense Weapons, by definition, utilize specialized armor-piercing rounds. Without those rounds (such as the MP7's 4.7mm), it's not a PDW.

Submachine guns use pistol rounds.

Ergo, the MP7 and P90 aren't submachine guns whatsoever.