It looks like it's just because they had no way to test, and bandwidth to deal with it. But should still mostly work, once whatever issue (that sounds like app notrization) is fixed.
It seems like the better option would have been to fix whatever was blocking them just two years ago, rather than this wild rube goldberg machine of a Linux VM emulated in a browser tab.
I mean, anyone is welcome to do just that! But I guess coding Rube Goldberg machines in JS (to push the boundaries of the web) is a thing I really kind of enjoy.