Yes, they are not completely random, but users may perceive them as such. Technically, nothing on computer is truly random.
Non-technical users don't configure active hours usually. Many are not even aware of this feature.
I'm not sure I would call a feature that can (and does) cause data loss, when user doesn't follow minor update schedule, only inconvenient.
The three cases I mentioned, none were using Home edition. 1st was sister's co-worker that was running some heavy computations of the terrain they were analyzing. He left workstation running over night, expecting to get completed results the next day so he could continue working on it, but system restarted and he lost one day, because he needed to run it again during the work hours. 2nd was a friend writing master's degree. She had all her research documents opened at relevant positions while she was going slowly through the research while writing. She put computer into hibernate mode each night, so she could just resume where she left of next day. Same story, Windows rebooted, closing a few dozen documents. Fortunately, she had her work saved, but she still lost her state/organization of documents and needed to find relevant section of each document again. 3rd was an accountant who was working late and left computer for a few minutes. Again, Windows restarted closing everything. I find current design of updates and active hours very narrow minded. It may seem good in theory, but from my experience, it's bad in practice.
But hey, maybe Windows is not intended for professionals any more. Just home users and gamers.