Maybe they didn't want them to find out that the police knew what they were driving, cause them to murder a driver and steal a different car to allow them to getaway.
Good point, I hadn't thought of that. But then they have to go out of their way, and might make mistakes. Murder and car theft would give the police and the public a new and specific lead.
Using the license reasoning, the police wouldn't release the purple car report either, since that also would motivate a car theft. Yet when they did, they got the guys in 1 1/2 hrs since the public fianally had the info. The info got to the public faster than the assassins could react to it.
But even then, they didn't release the plate number at the conference. Only a renegade leaker got that info to the media. I don't know if the trucker who found the duo had the license number, and if he would have called 911 without it.