This is a deliberate decision to force people to turn off tracking protection.
No this is a hilarious fuckup where they forgot to move twitter.com, pbs.twimg.com and more off of the Twitter domains, so Firefox started blocking it because to Firefox it looks like Social Media trackers.
Mozilla already pushed a fix.
It is essentially just extra maintenance of a feature in Firefox that (statistically) not many people use
As such, it's marked as "unsupported" to make clear that if any issues arise, Mozilla won't help you with those issues.