Apple Maps is absolutely very late to the game when it comes to road closures. Google Maps somehow always knows which roads are closed, even if for a few minutes.
Because users on Waze report it to them for points
Apple Maps does have the ability to make the same reports, but its super buried so I doubt many people even know its possible, let alone where to go to do it.
Also, I'm not sure but if a road that normally has several cars a minute goes to zero cars in five minutes say, it's likely it's blocked.