Just to show this off.
I was running some programs on my Amiga 1000, while I encountered the error seen in the attached photo. The layout is just like the Guru Meditation error, but with custom text.
Don't know if this kind of errors are seen in other programs, but I had never seen the "unrecoverable" red -bordered errors being used as anything else but the Guru error.
Program in question is/was Textcraft 1.0, and the error was due to minimal amount of RAM that was available at the moment. The error was hardly critical as pressing either mouse keys simply closed the program and caused no restart. Nice type of red-border error, for a change!
It's easy to make alert requesters say anything you like, I used to have a program in my C: directory on my Amiga back in the day that you could make custom ones with. But I suppose not many coders used them, as simple requesters were less intrusive and alarming.