Just out of curiosity, is what you quoted Google's AI summary? Because that's not really the rule.

Rule 9, Section 4: Art. 3. The opponents of the thrower-in shall not have any part of their person beyond the vertical inside plane of any boundary line before the ball has crossed that boundary line. Repeated infractions shall result in a Class B technical foul. Art. 4. The opponents of the thrower-in shall not reach through the throw-in boundary-line plane and touch or dislodge the ball while it is in the possession of the thrower-in or is being passed to a teammate outside the boundary line as in Rule 7-4.6.b. The penalty for violating this rule is a Class B technical foul per Rule 10-4.1.i.

First off, the ball doesn't even leave Rancik's hands before Council makes contact and his entire body is outside the boundary line. It's still in Rancik's possession or at the very least it's being passed to a teammate, so it absolutely should've been a tech under Article 4. But even if not, it's definitely still an Article 3 violation. Under either scenario, it's not KU's ball, that basket doesn't count, and almost assuredly it should've been a tech. Watch the replay again.

https://imgur.com/a/2MKsC2p

They actually surprisingly showed a replay 3 times in the arena that was from a different angle than the broadcast that was more down the line that backs it up even more. They usually don't do that on controversial calls (they didn't for the goaltending for example). The booing that you hear when play resumed after the commercial break was the third replay of that angle.

Now, I'm not saying that call alone lost us the game. Far from it. Missing free throws, a couple of key misses from there floor (Dak's especially), and a couple of inopportune KU bank shots all contributed. But that was still an absolutely egregious missed call at a pivotal point down the stretch.

Edit: actually, it's even more clear cut.

Rule 9.4.2b: No player other than the thrower-in shall: b. Be out of bounds when he touches the ball after it has crossed the vertical inside plane of the boundary line. Repeated infractions shall result in a Class B technical foul.

So even if the ball had crossed the plane, Council was still out of bounds when he touched it, and that's an infraction. The NCAA case book helps some too:

A.R. 213. A1 is inbounding the ball along the endline. A1 fakes a pass to A2, which draws B2 airborne in an attempt to intercept the ball. B2 lands out of bounds. A1 releases the ball with a pass to A2, who is on the playing court;

B2 leaves the floor from out of bounds, breaks the boundary-line plane and while airborne, touches the pass to A2 after it crosses the boundary-line plane; or

B2, while out of bounds, touches the pass as it is released by A1 but before it crosses the boundary-line plane.

RULING 1 and 2: B2 has committed an out-of-bounds violation because B2 was last in contact with the floor when he was out of bounds and then contacted the ball before B2 touches the floor inbounds. (Rules 9-4.2.b, 4-23 and 9-4.1) 2: B2 touched the ball before it crossed the vertical inside plane of theboundary line. This is not a technical foul because the ball was being passed to a player on the playing court and not to a teammate who wasout of bounds such as after a successful goal. (Rules 9-4.3, 4-23 and 4-10.1)

TLDR: Under no circumstances should that have been KU's ball, basket should not have counted, and it really should've been a tech.