Firefox 74 (currently beta) has some new kind of container tab sync in dev, perhaps?

It doesn't mention it in the patch notes, but I got a green "NEW" on top of my Conex toolbar icon on MULTIPLE Windows PCs. I was excited to see it because I thought perhaps Conex had a new update (it's been a long time). After clicking it, I was asked me to sign in to Firefox Sync again (which I was already signed in to) so I thought perhaps it was some kind of phishing scheme.

Has anyone else gotten this? Whatever it is, it doesn't appear to currently be working.

I know raising an issue probably isn't the best place for this, but I didn't want to amend the Wiki just for this type of question.