Nope. I have four ducks who practice (& do the real thing) mating.
The area looks like one of my ducks who was on the bottom just had the neck nipped and held down for the mating.
And they take turns acting as the wingman for each other. So sometimes two ducks are nipping the neck at the same time.
The neck recovers quickly.
I think if the duck was being picked on, he would be missing feathers in other locations like his tail, not eat or drink, and be by himself most/all of the time. He wouldn't talk at all. He would hide. You would be able to feel his misery ten feet away.
You'd see the and feel the other ducks aggression towards the guy duckie. You would see them chase him/block him/isolate him.
With what you have described, none of that is happening. He sounds happy and healthy. The whole mating thing (again, for ducks, the gender doesn't matter when practicing) is normal.
When the duckies mate, one bites the back of the neck, climbs on top, pushes the head down towards/into the water, the bottom lifts up tail, and the top moves tail downwards (sometimes coming in from the side). Top duckie falls off or gracefully gets off. If they think mating was successful (even if it wasn't) they do victory laps and splash A LOT!
I think your guy is fine. Keep an eye on him, but don't worry too much.
My girl Ellie is the fav for mating with Chocolate. When she needs a break, she leaves the group and isolates herself but is always within visual distance of the gang. Sometimes she is right next to them with a fence separating them. Those two are my most "active" ducks.
