I highly doubt it's Trump's official Nostr account. He's wants Truth Social to succeed so I doubt we will ever see him on Nostr. Nostr after all will bankrupt Truth Social.

Someone probably made it as a bot account that pulls automatically his posts from Truth Social.

I'm following it because it is extremely useful. It means I don't have to go check his official truth social but I still take into account that they might manipulate a post in the future. Verify, Don't Trust.