I'm a newbie, but this sounds about right to me.See it could be he finds them very enticing and just wants to mate them. I know a few of my young boys will chase girls to the ends of the earth. The pullets that give in easily get the dance, the ones that run.. well if they catch them, there is no dancing done.
Our roo started by chasing the heck out of the australorp girls. He didn't seem to have much interest in the others. He'd get the itch, and take off running after one poor girl, chase her all over the yard, up, down, over, under everything. Eventually he got to the point where he could actually catch one! And for about a week he'd just do his thing on whatever body part was under him. The poor girls were SHOCKED!
About eight weeks later now, he's actually tidbitting and doing other (NICER!) things to get the girls to come to him. And the girls have started laying, so maybe they don't mind his attentions as much as they used to?