You are taking it to the other extreme. Sure, in 8 hours I will not write something "unusually beautiful". But if I spend two hours solving a problem and hacking together a solution, I come to better understand both problem and solution. Hereafter, I then can rewrite my solution in another couple of hours and improve it significantly with respect to maintainability, readability, naming, messy choices, &c.
If I want this job, I would spend this extra time to submit this better solution because obviously that will improve my chances of getting the job. But that means that these take home assignments might not be such a good indicator of efficient proficiency. You might be overvaluing people spending more time on these tasks and undervaluing people spending the allotted time on these tasks. For example, a better developer who did write a solid solution in under 2 hours might get passed over because her solution seems not as good as mine where I did spend another hour to rewrite my initial messy solution.
If I want this job, I would spend this extra time to submit this better solution because obviously that will improve my chances of getting the job. But that means that these take home assignments might not be such a good indicator of efficient proficiency. You might be overvaluing people spending more time on these tasks and undervaluing people spending the allotted time on these tasks. For example, a better developer who did write a solid solution in under 2 hours might get passed over because her solution seems not as good as mine where I did spend another hour to rewrite my initial messy solution.