I don't believe this rumor but it is an interesting argument. No, Williams is not going to help the Cowboys in 2020. Nothing would. But he is 22 and has 3 years left on his rookie contract so getting him would be like making your draft pick today instead of in April. Even if the Cowboys were lucky in the 2021 draft and a top DT falls to them i the 2nd round, he is not going to be effective in 2021. Look at the top DTs taken in 2020. Brown and Kinlaw are fighting for playing time. Probably the most effective DT coming out of the 2020 draft right now is Davon Hamilton. He is not dominating but he is plugging the gaps because he is big and strong. Quinnen Williams comes with experience and is ready to reach his potential now.
If the Jets are foolish enough to give him up for a 2nd round pick, even a pick in the top of the round the Cowboys would be dumb not to make the deal. Then they can use their first pick to either trade down for more picks or to grab a LB who can actually make plays.