Apparently in basketball there is a potential unfair advantge to be gained by switching jerseys, and there are rules to prohibit doing that. There is no advantage like that in football. Both numbers, in this instance, are eligible numbers for forward pass receiving (provided they're lined up in an eleigible position) and the defense has exactly the same objective, whoever is wearing which number.
If # 11 has the ball, the object is to stop his advance. If # 33 has the ball, same objective. If one brother had an USC penalty called against him, and they were switching jerseys to minimize the possibility of that player getting a second one, and therefore being disqualified...but that's a real stretch, in which case NF: 1-1-6 provides the capability to deal with.