I have not seen a single credible (or non credible, tbh) mock that has him as a lottery pick. I’d love to see your sources on that, because there is a zero percent chance he’s a lottery pick.
He does have an inch and 4 pounds on KC, if you look at both of their listed college sizes. That’s not much when you’re looking at a lead guard in the NBA that’s around 6 ft tall. They’re both tiny. Tahaad definitely is more athletic and a better scorer off the bounce, but it’s extremely hard to see anyone taking him in the first half of the 1st round when the track record of guys that size succeeding is so rare.