The SCOTUS says in US vs Banks (2003) that only a 10-15 second wait between announcement and entrance to a home is sufficient. This hardly gives time for me to run to my window and see the squad cars outside. (assuming there are squad cars.
Your post implies that the Court said 10 to 15 seconds is sufficient for all knock and announce warrants, but that is not true at all. In fact they reaffirmed the concept that, "This Court has fleshed out the notion of reasonable execution on a case-by-case basis . . ."The SCOTUS says in US vs Banks (2003) that only a 10-15 second wait between announcement and entrance to a home is sufficient.
undercover cops
Short of a "the hostage is gonna die NOW" scenario, I don't see any basis for "undercover dynamic entry" - do you?