That's definitely fair, and I assuming in a classroom setting you'd be very consistent and precise about what that means. But this is a twitter poll, and I doubt people are that consistent. Ultimately I'm just pushing back on the conclusion that this is because "Bayesian thinking is really foreign to people."

I think if the question had instead been "would you bet on the urn having started out with more red balls, green balls, or equal number of balls" the distribution would have been very different.

You have an urn of 50 red and 50 green balls. Roll a die and add a red ball for every pip. What is the probability of the next ball you take being red?

I say both can be a question in Statistics I where you calculate probabilities based on combinations.

So I'll say it depends on the level of education for how the question gets interpreted and saying those who never took Bayesian reasoning and consider n unknown are wrong gets elitist.

Not known, but certainly defined. It has to not be zero at least, otherwise you couldn't take out a red ball in the first place. Or at least that's how I understand this problem. You don't know what number n is, so you need statistics or simulations to grasp the probability of the color of the next ball.

Another way of making your point: it would also make the information about the distribution of n irrelevant, so it's a bad interpretation of the question.

i personally would throw out the question if i was a teacher. i still feel it's ambiguous