From a hiring standpoint, the problem imo, is that employers set the timebox thinking that it means something when comparing candidates' solutions. I couldn't care less whether somebody spends two hours or two days on it. I want to see the best solution somebody can produce. I have engineers that can do things quickly and others that can do them more slowly, and both are infinitely more valuable to me than someone who can't provide a quality solution under any circumstance. In my experience, if you're filtering out the slower engineers that produce quality work you're going to be in for a very long hiring process and miss out on a ton of great engineers.