I case I was unclear, the setting I'm talking about is totally different from the bug report linked by OP. For that: I have never seen a popup appear when closing a tab in Firefox so I suspect it was already fixed long before Chrome (and I haven't changed anything related to that in about: config)! But I haven't been about to find any definitive source about it.
I believe closing gmail browser window while composing a message would show a popup.
I use it in an app where editing an item locks it for everyone else and to unlock it, one needs to save or cancel the edit. So closing the browser tab while editing shows a warning.
Edit: I was corrected by the comment below. Had in mind a different function.
A kiosk at a gov/hospital that needs a browser open on a default page?
Their are probably better sys admin/mgmt tools available though.
With the "user.js" feature [0], you can actually control them from a flat configuration file.
They are seriously afraid to even use it normally. Expecting them to change configuration is utter bullshit.
Older people are not a special case of a class of people incapable of becoming proficient with technology.
Current older people are in the position of having grown up before computers.
For any given tech product the computer incapable are probably not your biggest segment and that segment will shrink over time.
All of our 80 year old grandparents who mostly don't use technology now will use even less in whatever afterlife awaits and pretty soon we will have 50 year olds who encountered computers in their teens and grew comfortable with them.
Seriously, people can configure things. But on their level. So a ordinary person is able to configure popups yes no and might understand the consequences - but if this setting is next to experimental new webgl module which might crash your browswr - and hundreds of other very technical ones, then clearly no. And firefox about config is lile that.
If a behavior makes sense and no one would reasonably not want it (like blocking popups during page unload), why does it need to be an option? Why isn't it just "the way the browser works"? What other "unbreak my browser" options are buried under there?
The option discussed was forcing new windows into tabs.