All MMORPGs do it at this time and the reason is because, quite frankly, most people do not play at this hour:
- NA are sleeping.
- EU it is very early morning and if they are awake, they are probably at work/school.
- JP it is not quite peak hours yet. Almost is.
- OCE peak hours would be in an hour or two.

So this time cleverly avoids those peak hours and the timing itself makes sense.

SE did say there have been too many emergency maintenances though. They wanted to put a stop to that. Unfortunately they didn't succeed yet and the patch has had a lot of bugs from what I've seen people say in the game. Whatever they are doing to address their internal QA issues, it hasn't worked yet.