They're called standups for a reason: you're supposed to do them standing up so that people whine if they go over five minutes. That tracks out to 25 minutes or less than one-eightieth of your week.
The deep flow disturbance can be caused by any sort of communication. So basically, that’s an argument against communication, as opposed to being an argument against standups.
If anything, by being at a fixed time, either at the start, or the end of a team’s day, it’s far easier to prevent a standup from disrupting deep work than a Slack message would be.
Except async communication doesn't disrupt deep flow if done properly since it should be simply ignored until flow breaks or pauses naturally.
A slack message won't disrupt my deep work because I'll have notifications turned off, unless it's extremely urgent in which case it would be too urgent to leave until a standup anyway.
This is just not realistic, a standup of 7 or eight people will take minimum 15 to 20 minutes, from the moment that you leave your desk to the moment you get back.
Some standups go off track, and if you count everything you are looking at close to a third of a morning per week or so.
I've had teams bigger than that with a fixed 10 minute slot for standups, where the next team would have their standup after those 10 minutes. It was not a problem, but it enforced meeting discipline.
As for going off track, you will need to learn to tell people (including yourself) to take a time out and discuss matters after the standup. If anyone says more than a sentence or two, and if there is more than a single counterquestion and a short answer, then that should be taken after the meeting.
Obviously this is just my experience, but in my office of 13 (11 devs, 2 managers) our stand ups take 5-7 minutes (on exceptionally rare circumstances it’ll take 10 or 12, but that’s normally due to large production issues).
They are useful for knowledge spreading and understanding what everyone is working on - we switch projects quite regularly so it’s quite nice to have a birds eye view of where each project is.
It's an illusion, most people don't have a good sense of time. Just getting everyone in a room and waiting for the last person to arrive and everyone to leave, grab a cofee and start working again is at least 12 to 15 minutes for that amount of people.
Next time you have a standup, look at the clock once you get up to the standup, or that you stop working normally and start looking around to see when people are leaving to the meeting. And then look at the clock when you are back at your seat working again.
People start getting ready to the standup 5 to 10 minutes before, chatting while waiting, etc. Count the time that you have stopped working normally, where you can't do any large task because you know there is a meeting in 10 minutes.
Don't just count the time literally from the moment a person starts giving their status to when the last person finishes, as the real overhead of the meeting is not that.
I guarantee you if you do that systematically and count the complete overhead and not just the literal overhead, that at best it will be typically 15 minutes and for longer sessions half an hour.