Unfortunately... it can. Which I can say on the basis that, it did. There were no schedules or filters set in the settings for do not disturb and I don't know of any other way to deliberately cause it to activate. If there's more settings somewhere perhaps there some additional sets of rules and logic that would explain why this happened, but even if so, they never had any personal involvement from me.

In any case though, I had found the article you linked already while googling but in my frustration I must not have read very attentively because I misread the option clicking method of setting or disabling the focus state, and was option clicking on the moon icon instead rather than the time and date. Clicking where I should have worked, as did the suggestion from another user to use the switch in the control centre. The strange thing is that after trying both of these methods successfully, the far more intuitive and obvious method that I tried right from the start unsuccessfully, now started working. Prior to disabling via option click, and also through control centre, if I clicked on the crescent moon icon I would be presented with a list of focus states, of which my system seems to have only the one, 'do not disturb', while I could find no off switch it did seem that the most obvious form of toggle was likely to be clicking on the 'do not disturb' text since that was apparently the mode that it was in and it stood to reason that would likely toggle it off, except, it didn't do anything hence my utter confusion. Now it just works as you'd expect and I now have 3 ways to turn it on and off. The fact that that button just didn't work is about as explicable as why the focus state tripped in the first place through no actions of my own when you say it isn't supposed to do that.