> "They will reject" seems an awful like "won't run on my distribution", and not because it's not compatible because of runtime or kernel differences, but because of its 'being nonfree'.

It doesn't sound like "won't run on my distribution" to me. It seems that you intentionally took this line out of context just for the argument (or to defend MS).

The full paragraph:

> These distros are ready-to-use full systems whose developers have made a commitment to follow the Free System Distribution Guidelines. This means they will include, and propose, exclusively free software. They will reject nonfree applications, nonfree programming platforms, nonfree drivers, nonfree firmware “blobs,” nonfree games, and any other nonfree software, as well as nonfree manuals or documentation.

Next paragraph:

> If one of these distros ever does include or propose anything nonfree, that must have happened by mistake...

"This means they will include...". Not "This means they will run...".

"include or propose...". Not "execute or install...".

It clearly means that they don't include nonfree stuff with their systems. Not they don't allow nonfree stuff to run.