It's true, we have no idea what their numbers are. But as far as wild encounters with their true form go, there have been very few.

[He has to take a moment to consider that last bit based on what little he knows about the two Pokemon.]

I cannot confirm it for certain, but it could be possible? If they can mimic other Pokemon well enough with their illusions, it's not an extremely far stretch to consider object materialization. It all depends on how far they can take their ability.