On my old Windows 7 it still works. I cannot anything newer, I never will use any Windows version beyong 7.
I guess our issue tracker will tell us when Batch files are not supported any longer, each time a user uses @elextr's great build system commands, a Windows batch file is created and executed (https://github.com/geany/geany/blob/master/src/geany-run-helper.bat) :D.
And since we already have the filetype and @techee did already the work, why not adding it?