You have a common misunderstanding of what is meant by "time horizon".

This is not "how long does AI take to do ${thing}", it is "how long does *human* take to do ${thing}, where ${thing} is from the set of things that AI has probability = n of getting right", where n happens to be 50% or 80% in the METR studies.

At least, that's the short answer, here's a video with more depth: https://www.youtube.com/watch?v=evSFeqTZdqs

My experience is the AI actually completes the task in a few minutes, when it was a 2-ish hour task and the AI has a time horizon of 2 hours at P(correct) = 0.8. It is I the human, not the AI used by me, that would have taken 2 hours.