If you're already time constrained to the point working 2 extra hours means you can't get through the day without caffeine and skipping meals then of course it'

If you're already time constrained to the point working 2 extra hours means you can't get through the day without caffeine and skipping meals then of course it's a bad idea, but that's not an inherent fault of a 4x10 in itself. A 4x10 is particularly attractive for those able to work remote and/or without lots of other time commitments. If you have an hour commute each way, kids to drop off/pick up from school/sports, responsibility for cooking meals 100% of the time, and so on then it really doesn't make sense to point the finger at the 2 extra hours as the sole root cause of the problem in that situation.