It's also a weird thing to say, given how much more difficult GitHub PRs make contributing regarding actual barrier-to-entry. GitHub contributions are only easy if you're already using GitHub to do your work. Talking about the marginal difficulty of using GitHub as if it's low on an absolute scale (rather than a relative scale, which is what marginal difficulty is about by definition) is like talking about the benefits of any other heavily subsidized thing without acknowledging the hidden subsidy and factoring it into the absolute cost.

I.e., it can only be called a low barrier to entry if you're willing redefine "entry" to be something other than "entry".