The difference is that in most places over here, smashing into someone's home unannounced is an almost sure way to get shot by the residents of the home. That was the case here. They smashed into the apartment after midnight and her boyfriend understandably opened up on them.
And that they were plainclothes police. That part seems pretty crazy (maybe not true?). Why wouldn’t you want to clearly marked as police in the middle of the night?
A few reasons:
1) If you think the community is hostile to police presence, being unmarked prevents the community from doing anything to warn the suspect of their presence - or to just plain shoot the police, which is occasionally a problem in the USA. Since people getting changed in a car in the middle of the night is likely to cause problems, that tactic forces the officers to continue to be plainclothed until they have an opportunity to change. (This, I think, is the most likely reason. Or at least what the bosses who approved the venture were told).
2) If police think being unobtrusive will help them gain the trust of the occupants, it might make their search easier and/or less dangerous. Of course, no-knock tends to render that pointless...
3) ...but if they obtain entry without alerting the occupants, they might be able to do the search without waking the occupants up. If they are lucky. I'm not saying that's legal, but it's possible that might have been in the officers' minds.
3) To exert priviledge. Plainclothes is usually an earned privilege, and expressing that can have a certain in-group social value.