This is more likely to be the hotel's fault than Booking's. You'd likely have the same issue with any third party aggregator. Many hotels (much like airlines)

This is more likely to be the hotel's fault than Booking's. You'd likely have the same issue with any third party aggregator. Many hotels (much like airlines) regularly overbook as a business decision, and third parties don't really have any visibility into this kind of thing. It's less likely (but not impossible) for this to happen to you if you book direct, and it's helpful to inform the hotel if you're going to be arriving late. Plenty of reasons to dislike Booking, but this particular one is more of a systematic issue.