The party honchos don’t need him out there lying about Social Security, or anything else for that matter. They’re perfectly capable of doing it themselves
The party doesn’t want him making up his own messaging. Nor do they want it to flub their message if he tries to toe the party line. They are angry mostly at themselves but they did this to themselves.
But he’s a free American he can say what he wants when he wants pretty much wherever he wants.