Why did they need to have guns drawn and that many cops, even if the flag had been correct? A car involved in a homicide investigation doesn't mean it's even being driven by the suspect. It's not a positive ID at all
This training is supposedly for "officer safety." But being a police officer in the US isn't even in the top-10 most dangerous fields, and the vast majority of deaths are from traffic accidents or health issues while on the job (e.g. heart attack/stroke), not gun-related. So it is more likely a cultural issue within the profession.