There were no specifics stating it would work, however there were absolutely no reports of incompatibility with the 11, and the fact that the new keyboard is compatible with gen 1, 2, and 3 of the 11 you should have no issues. However the same caveat could apply if you use a screen cover, if you don’t I think you’re good to go.
Actually looking at the specs only the 12.9 iPad Pro has the thicker .5mm screen. So there shouldn’t be any problems at all.