don't give it another thought, keep doing what you're doing, my first two vizslas, I did the same thing with a dummy made of rooster feathers, all but the head and feet wrapped around a sock full of kitty litter type stuffing!
my kids would plant it in some bushes and I would work the two pups into the wind and like yours, they'd find it every time, they didn't go on their first point, which was in a hunting situatian until ten months old. That is to say, other than flash points at a wing on a string or maybe a tweety bird in the backyard!
try the wing on the string routine, tease the pup with it, don't let him catch it, until he locks up! should only take a couple of sessions before he does it!
here's a photo of my pups my girl whelped last August, they were about five weeks old in these photos.