Exchange of federal land for private land the government wants elsewhere is not new.
It is often done and usually makes the federal boundaries smoother.
83 acres is not much. The article does not say how much the federal government gets in the exchange. It might be two or three times as many acres.
I don’t believe it’s lawful for any POTUS to sell federal lands. Congress has the authority over selling Federal land. And why should someone rich dude get to put in a private road into Yosemite?