Given that this question is about humans, and discusses their behavior, it's clear you are making some assumptions about the structure of the question which are not present in the question.
That's certainly a reasonable thing to do.
What's not reasonable is to assume that the assumptions you make are going to match the assumptions of others. Likewise, when make assumptions there is a chance that the assumptions you make are incorrect.
That may or may not be the case here.
But the fact remains, you need to make some very strong assumptions for what you have said to be true.
You are correct, that the participants are people, with birthdays, and capable of speaking, is an assumption. You appear to be taking issue with that assumption. I suppose that is your prerogative, but it probably leaves you in the vanishing minority.
That's certainly a reasonable thing to do.
What's not reasonable is to assume that the assumptions you make are going to match the assumptions of others. Likewise, when make assumptions there is a chance that the assumptions you make are incorrect.
That may or may not be the case here.
But the fact remains, you need to make some very strong assumptions for what you have said to be true.