But that's literally what canon means.We need to stop with this 'on screen only' canon nonsense.
The only new thing is the format. Obviously no one posted things on social media back in the day because social media didn't exist. Facebook and Twitter weren't mainstream until a few years after Enterprise ended. However we still had people involved in production establishing stuff in other sources, reference books, interviews and the like. Hell, the head writer and co-creator of Voyager even wrote two Voyager novels. But they were never considered canon because they were not on screen. The same applies today in regards to whatever someone in production has tweeted.With production personell now directly dropping factoids on social media, etc, it's time to grow up and accept official word as canon.
Besides, even production personnel posting things on social media can still be wrong, like John Eaves and the infamous 25% thing. Best not to take anything at face value just because it comes from someone who works on the show.