>> Like what's the point of having the test be time constrained?

A few examples: competitive tests based on adapting the questions to see how "deep" an individual can get within a specific time. IRL there are lots of tasks that need to be done well and quickly; a correct plodder isn't acceptable.

That makes sense to me, but in that case I also just don't understand why one group gets more time than another group. If the test is meant to evaluate speed, then you can't give some groups more time, because now it doesn't evaluate speed anymore.