I also suspect tiny homes probably are a bit too tiny. I'm not sure if the extreme tinyness in a political statement, or just social signalling that its a choice, not that they can't afford a bigger house. I would predict though that if the movement has legs, tiny houses will get much less tiny.
The details will vary of course but so many of the discussions seem to be around whether you "can" live this way, not whether you want to, especially long-term.
I say this as someone who lives in a fairly modest-sized house but enjoys not feeling I have to squeeze every square foot out of my space.