According to one of the articles, "the most volatile period is 16:00 UTC / Noon EST / midnight CST on a Wednesday." During this particular hour, Bitcoin is said to be "36% more volatile than the average of all time periods." Moreover, Bitcoin is "least volatile period is 8:00 until 10:00 UTC on Monday."
Which means if one live in a different time zone, it will be affecting or crashing.
For them to conclude in this, I am guessing they might have monitored it for a year or more.
Personally, I feel this sort of thing is hard to monitor considering people's emotions are also a contributing factor and this have no timezone.
I think if you live in a world of global time zones and global deals that you do, you could sleep or wake up according to what you need to do. People need about 6-8 hours of sleep most of the time, sure you could live with less or you may want more but 6-8 hours is ideal and that is how it should be, meaning if you live in a timezone where you need to be awake from 1 AM after midnight to 7 am in the morning, you could do that, sleep at 8 am in the morning, wake up about 2-4 pm in the afternoon and just keep living like that forever, it is really not going to change too much of your life.
When you are hanging around with your friends that usually ends before 1 am anyway (and not even happening now because of covid) and people usually do not meet up early morning neither, so you could have all the things you want in life while still sleeping on early hours and even afternoon so time zone could be arrange according to whatever you need.