OK, I was washing it out and most of the water was coming out the end, rather than the holes along it. The hole looks possibly 'homemade' too rather than from the factory.
Neither of my tetra 700 & 1200 have a hole in the stopper,unless someone wanted to slow the flow down...
If you want a better flow out of the spraybar i would put a blob of aquarium silicone in the hole
Is the flow not dictated by the motor rather than the size of the hole? If you block the end then the pressure will increase and force more water out of the holes along the spray bar.