> There's a specific reason why they do this and ask you to make a decision in an instant. It's called accommodation.

You are right. It can be an issue in the other direction though.

People are checked after often sizeable waits looking at the same thing (their phone, the wall, outside) for a long time.

When you then start the switching lens tests, there will be a set of lens optimal for your current situation, and a different set of lens that would fit better for a long day of doing whatever you are usually doing with the glasses on.

Knowing how good a pair matches after accommodation is equally valuable, IMO.