I guess it's trying to be a bit clever - it's a 'medium' as in a 'media platform', and it's a 'medium', or tool for 'medium-length' posts, rather than Twitter's ultra-short length.

I can see how they must have thought at the brainstorming session that they had a backslappingly cool zinger that worked from every angle.

But yeah, it ultimately sounds a bit meh. Especially in the land of supersize.