During the draft, why are draft rights traded and not draft picks?

Question

If I remember correctly, during the NBA draft and maybe even the NFL draft, if teams trade picks, they can't announce the trade until both teams have drafted their respective players. Only then can they announce the trade.

I read somewhere that before the draft, they can trade picks and announce on the news. During the draft, they can only trade draft rights and not draft picks. Why do these league do this? What is the reasoning for this?

Answer 1

One reason why draft rights are traded in the NBA are because you're not allowed to trade consecutive first round picks. I.e., if you trade your only 2020 first round pick, you must make a 2021 first round pick - you can't trade it. However, you can make the pick then trade the player's rights.

Second, on draft day, picks can only be traded until 2:00 PM Eastern Time; after that, they must trade draft rights.