As long as they retain the option to disable certain features on a repo, I am wholly in favor of consolidating the development stack into GitHub. Easier to mandate 2FA and other security procedures when your team doesn't have to juggle several sites.
Friendly aside: the expression is "err(s) on the side of..."
Zeit's was the most active spectrum community I was part of, interesting they're the lead tester community for this new GH feature.
Spectrum fell between a number of posts, it was never really "chatlike" so it looks they've gone completely in the forum direction with discussions.
https://spectrum.chat/spectrum/general/spectrum-is-joining-g...
But I would caution against integrating too many tools into GitHub. As a user, I like that GitHub errors on the side of saying no. You don't want to end up with a bloated product.