Because he'd have plausible deniability that the posts weren't really him and they'd have a hell of a time figuring out who to contact to stop the posts. If they're taking away visitation completely then that's a different story.
Discussion
He could do that on any other social media, even twitter with a different account. I don't think there's anything about nostr that help a man deprived of his basic freedoms.
If it was illegal, another social media would be forced to stop.
If Ross had nostt account, it would quickly gain popularity, get noticed and they would make him stop. It does not matter how censorship resistant the network is if they can just forbid him.
Any other social media would be readily compelled to shut off any account suspected to be him. It's not a silver bullet, but nostr would help