Yes this would defeat it, but standard practice is that you can keep betting a couple rotations into the spin. The reason for that is that some people believe the croupier can target his shot to some extent. (I don't think it's farfetched that someone who spins a ball 8 hours a day could get above chance at targeting.)
I believe the croupiers also have rules on how hard they must throw the ball, in addition to rules that define how long they have between picking up the ball and throwing it. In the first case it’s usually at least 3 full rotations, and in the second case it’s before the spot the ball was pick up from passes their hand.
I don’t think a croupier can meaningfully cheat with these rules, especially since they’re not on the hook for people winning too much. If they could cheat I think most would cheat against the casino.
Leaving the bets open while the ball is spinning causes a lot of players who think they can time the ball (or as another commenter said, believe the dealer might be cheating) to bet and presumably yields higher profits.
There are other countermeasures developed nowadays, such as Cammegh's RRS (Random Rotor Speed): https://www.cammegh.com/our-products/roulette-wheels/mercury... - essentially after bets are closed the wheel is able to ever-so-slightly slow down at random times, throwing off any prior calculation.