This did not work as intended. I wanted to provide an update for users of the experimental version without affecting users of the stable version. Apparently the mod manager still downloads the update for everyone, even if the condition is not met.
I have removed the update for now.
If you require "base >= 2.0.27" then it will only be downloaded for players who have that version or greater. Doing "space-age >= 2.0.27" does not have the same effect.