That is a method. So far prosecutors have a poor record actually convicting someone for using handloads. However, that doesn't mean that it doesn't cost you time, energy, stress, and money, to mount your defense.
The first question I have to ask is: Is the potential lawyer fees really worth the 25 bucks for a box of whatever the police in your area carry?
The second question I have to ask is: if the police load groups 5 inches at 25, and your handloads are 1.5 inches at 25, does that really matter in a defensive pistol situation?
I guess if you are truly concerned more about bullet performance than any other factor, and aren't worried about being able to pay an attorney to defend yourself from an aggressive prosecutor then your method makes perfect sense. I don't want anyone to get the idea that "using published load data" is a ticket to not being prosecuted (Mas Ayoob has served as an expert witness in several successful defenses of individuals who used handloads).
So, with all those factors to consider, I hope you understand where my advice comes from, and why using the same load as the cops is cheap insurance.
And anyone who is concerned about a cop load not being "lethal enough" needs to get an education on terminal ballistics. All bullets are lethal, and if you do your part the bullet will work just fine.