This is problematic for them, and coming from a 24x7x365 world, I feel their pain. There simply is no “night during the weekend” for them. If you, for example, are on the east coast of the US, at 3pm on a Saturday, that’s 10pm in Bucharest, Romania (where a lot of the engineers apparently are, as well as Ukraine). That’s complicated by having customers all over the world. In Sydney, it’s 5am. Once you have customers world-wide, there simply is no “down” time for maintenance. The best you can do is gather stats on traffic for the subject service and determine where its usage is lowest on a weekly basis, and do it then if you can, and sometimes, unfortunately, that means having one or more engineers working at 3am their local time. That’s life in 24x7x365.
I don’t recall seeing any announcements for this window. I’ve got some for prior (6/25), but nothing for today/Saturday anywhere in the world. That may be a #fail on their part. If it was emergency maintenance to correct a problem from the earlier 6/25 upgrades, they should simply announce that, even if the notice is an hour or less. Emergency maintenance is also an understood paradigm.