Wouldn't it be better to have students learn on hardware itself? I guess if the chips are write only or are too hard to flash it would make since. Or if cost was a limiting factor.
You can probably iterate more rapidly on the emulator; it's not like this and real hardware are mutually exclusive, just as using, say, an Android emulator in development and also real devices aren't mutually exclusive, but things people do together.
“Wouldn't X be better?” is only meaningful if the options are mutually exclusive.
A nice thing about MicroPython is that you only need to flash the chip once - at least if it has enough flash storage to support a file system. Once flashed, you can work on a REPL (over either UART or WLAN) and write files.