chance of entering the cylinder anyways. Like, if a guy shoots a corner 3 and it hits the side of the backboard and bounces back towards him, and the guy who was guarding him jumps up and grabs the rebound - even with the ball still above the level of the rim - that's not a goaltend because the shot has no chance of going in.
In theory, one could argue that Lillard's shot had no chance of entering the cylinder, and thus Gobert wasn't goaltending (but in which case he should have grabbed the rebound rather than swatting the ball).