Earlier quoted context omitted.
So, should there be apps that use it to transfer files between iOS, Android, Windows, and Mac without requiring them to be on the same network?
No WiFi cards for pcs support it.
I've definitely used STA and AP modes concurrently on my Windows laptop with the operating system's built-in internet connection sharing function to help troubleshoot a problem in the field.
That was around a decade ago. It didn't take any extra effort on my part; I just told it to do the thing, and then it did that thing.