It doesn't seem like this is a probability question so much as it is about the rules that govern the game show host. If he knows where the car is, and also gets to choose which curtain to open, then there is the potential that he is communicating with you. So, interesting question about game show tactics, but not about probability.
With three curtains, the reasoning is just the same...
And equally flawed. The original question is meaningless unless we know the structure of the game. If the host has knowledge, and gets to use it in the choice of which unchosen curtains are opened, then the question is just about Monte Hall's likely behavior, not about probability.
If the rules allow the host to choose, then we introduce factors which are not knowable to us. Are they over budget this week? Has the show run out of time? All fascinating gaming I'm sure, but not amenable to probabilistic analysis.