Yes I'm aware. The comment referred to widget removal in Big Sur though, and the only "widgets" I can think of that were removed were Dashboard widgets.
Big Sur/iOS 14 widgets don't support interactivity beyond single clicks, so I don't see any way a Numi widget would be of any benefit.
The calculator widget is no more. IIRC (I haven't looked into how widgets are built) there's no way for a calculator widget to work. They work in a way where the developer just gets to update some data on a schedule.
Yes, you are right about that. Apple doesn't allow it to work as a mini app. I suspect, they will unlock more APIs to make Widget more interactive on later versions.
If you were still using it I'm interested to know why – I stopped because it felt clunky to use and there weren't many widgets.
I'm not sure it's much of a criticism of an app if they don't have a Dashboard widget.