Thats the part I'm a bit apprehensive for, rather I'd be curious what led them down that decision for an emulator of all things. Or is it just a bit of portability and shader technical debt?

In general the way people make money off emulation is by selling it to iOS/Android users. In this case, it's free on PC and the Android version is $3. The emulator needs to be closed source for this business model to be feasible.