Information about their plans being in the wild but not formally announced adds all kinds of possibility for SEC involvement. You have to be very careful with how information is publicized to avoid insider trading or the appearance of it.
No, they don't. If you can't track where information is, the ability of people to act on a tip massively increases, and the enforcement is much more difficult.
They are effectively legally required to use NDAs when discussing future directions of their business. There may not be an explicit regulation you can point to, but when information is spread around without tight control and someone acts on it, the SEC can and very willingly does get involved. There's a reason it's effectively universal for any publicly traded company with meaningful legal representation, and it's because it's a ridiculous level of negligence to have those conversations without them.
Wouldn't it be better if they federated so it doesn't become a walled garden in there? It means we can stay on our own instances but aren't cut off from their large userbase.
(E: For perspective,) Truth Social was just a mouthy startup for spreading hate, not a nearly trillion dollar company with a lengthy history of anti-competitive activity.