The problem with this definition is that it's so broad it encompasses many many things that are never talked about as “emulators”. By this definition, Docker is an emulator, a VM is an emulator, an x86_64 CPU is an emulator (because it “emulates“, in the broadest sense, x86), a C compiler is an emulator (“emulating” the PDP-11 on modern hardware), etc.
Even your own quote reveals the issue:
> > That said, Wine can be thought of as a Windows emulator in much the same way that Windows Vista can be thought of as a Windows XP emulator
Yet nobody talks about the latest Windows as being an emulator for older windows …
In short, this definition is akin to defining humans as “bipeds without feather”, we definitely fit this definition but it's way too broad to be useful.
Even your own quote reveals the issue:
> > That said, Wine can be thought of as a Windows emulator in much the same way that Windows Vista can be thought of as a Windows XP emulator
Yet nobody talks about the latest Windows as being an emulator for older windows …
In short, this definition is akin to defining humans as “bipeds without feather”, we definitely fit this definition but it's way too broad to be useful.