This is ultimately an argument of semantics. Technically a wing player (at the 2 or 3) has to have very similar set of skills. However traditionally the 2 is meant to fall between the PF and the PG, leaning toward PG. More of a playmaker generally speaking, strong outside shooting, and speed. And of course the ability to guard the opposing team's 2. The 3 is traditionally meant to fall between the PG and the PF leaning toward the PF. He should bring length, strength, and generally a stronger inside/outside game than a 2. This is just basic basketball. From this standpoint you have wing players that can do both, but generally speaking most players fall into a natural niche. The natural 3 will have to alter his game somewhat when playing in the 2 spot, but he does this in order to 1) fill the role of the 2 in the offense (floor spacer, guard opposing 2, etc.) and 2) be able to bring his strengths to bear in that position. And vice versa for a 2 moving to the 3. Some players have skillsets and physical tools to match up well in both spots, but normally they still tend to play better at their natural position (Hayward is a decent example of this).
So yes, he needs to alter his game. And yes, he needs to play to his strengths. The system has little to do with what an individual player must do to play within that system. It does not remove or negate entirely the nature of the 2 positions relative to each other.