This is no longer the case. I've released a feature into production (still in beta and might need tweaking) that causes randomized NPCs to spawn disguised at random points in the city and walk OR sneak around to a destination before unspawning.
These NPCs will take all shapes and forms. It should make it less easy to identify disguised folks, because there are truly random people walking around disguised.
I will tweak this system and add a bit more to it and fix issues as they crop up. As always, all of you are on the front lines of this. If you notice patterns, or non-randomness in the NPCs (or suspected NPCs), please feel free to call it out here so I can correct it.