The one time I managed to get a license plate, the police claimed that without witnesses, they couldn’t do anything. ACAB.
It sucks but unless he hurt you, hit your bike, or you have any sort of footage what is the police suppose to do? Show up, he denies everything and that’s it.
If they could charge him on your claims alone, think about the scary consequences of such a “legal” system.
what is the police suppose to do?
Start a paper trail. If multiple unconnected bikers report them or they are involved in an accident later it is prior evidence of reckless driving.
Even if he denies it when police show up to ask questions it might scare him enough to stop doing it.