There is of course the issue of "Yes, but so what?"
The whole point of protections against police overreach is that they weigh the right of people to be secure from state intrusiveness more than police convenience, and by definition this will make it harder for police to do their jobs.
Well I think some crimes are serious enough that it's reasonable for police to be allowed to not disclose their presence and intentions before a raid or arrest because doing so would give the suspects a chance to dispose of or otherwise make evidence unavailable.