False. The US president that made Bitcoin legal in the United States was Barack Obama. It has been legal here since Bitcoin began.
If Bitcoin has always been legal and no one made it illegal, then no president can claim anything
Remember, this is the guy who issued his own NFTs. He didn't need to change the law to do that, he certainly doesn't need to change the law for Bitcoin.
Not to mention Trump has a history of just saying things he has no intention of doing. The president doesn't even have the power to make changes to bitcoin legislation, or any kind of legislation.
All US presidents can just go the route of Executive Orders aka "anything I say goes". It's not legislation, so doesn't require Congress approval, but it is law. It's not all-powerful but once issued can have immediate impact... if only to be overturned/challenged later.
That said, I agree with you, he'll do whatever he thinks necessary at the moment, there's nothing he gains from moving Bitcoin along from its current status as legal anyway, (though I can imagine one item he could make happen is to simply make it tax exempt to garner corporate support).