Which is pretty much every current OS and device except Windows, but yes. Microsoft holding us back again.
I still assume political reasons and it's a lose lose situation for MS. E.g. they either include Taiwan's flag and lose China's approval, or they don't and get a huge backlash from everywhere else.
PS: Firefox on Windows uses its own emoji font "Twemoji Mozilla" to display flags.
No font in Google fonts does, for instance. At least from their own little demonstrator. There is https://github.com/googlefonts/noto-emoji Noto Emoji which can render the flags but you need to build it yourself