Craze

Update: I tested the 2020 FPIU Valor mod as an add-on vehicle, and surprisingly, their police unit allowed me to pull over vehicles. Since the support team noted they could pull over vehicles, there may be an inconsistent issue with the FHP vehicles, but I've informed their support team of this development, and I'll stay in touch with the cause if possible.
 
Update 2: Further testing shows that some FHP vehicles can pull over vehicles, so it's likely a vehicle bug that needs fixing. Once the support team fixes it, I'll try to put the root cause here in case anyone else has my issue.
 
Update 3: This is fairly broad, but the support team responded and stated that the affected vehicles were not acting as police vehicles because there wasn't a light setting set for the police units.