This one never bugs out when you Alt-Tab. I guarantee it =D
Viewing post in Backdrop Designer V1.380 comments
You have plenty more experience with your own app than I do, so I'll take your word for it that it's stable. Still, I prefer not to risk the headache - never know how other apps might react to constant alt-tabbing into a fullscreen app.
Also, I can see the forced fullscreen being an issue for people with ultrawide monitors who prefer to nest windows side-by-side while working.