As with all of these things, it depends on your goal. Making NPCs as PCs as a matter of course isn't exactly wrong, but it's not how the game was designed so it causes a lot of extra work. If you're doing that extra work toward some purpose, then fine. If you're doing it because you don't know there's an Easier Way, then, well, it might be worth it to learn that way.
In the vast majority of cases, you don't need to make NPCs as PCs and the game will work fine. If you can't tolerate that NPCs and PCs are built on different chassis (even if they drive the same road and use the same fuel and all that), again, no one's going to stop you from making them the same. But the game itself isn't wrong for being built otherwise.