I agree that this may be the point. Software changes, and being able to compile with latest libraries is somewhat of a minimum requirement.

To Apple's defense, are they supposed to wait until the app breaks, starts receiving many complaints from customers, before it triggers the review process for them (which they would be forced to look at as somewhat high priority) before they then take action to remove the offending app? That hurts the customer experience from their perspective.

Better for them to institute a policy preemptively addressing these issues (arbitrary as the timeframe may be).

And four hours is a good chunk of time, but what percent of time is it compared to the amount of time for the app to be designed and implemented in the first place?