LOL, no. Competition shooters also buy powder in bulk by the lot number for consistency. Primers are less likely to have enough variation between lot number to make as much difference as powder. I'm not going to mention bullets, as we'll assume we're using match grade bullets.
Depending on caliber, for instance, .308, cases capacity makes more difference, which is why the volumetric capacity is measured, or the cases are sorted by weight, and the cases on either end of the spectrum are not used for accuracy, just the cases that fall withing a small spectrum are used. Next would be neck turning to get the pressure exerted on the bullet ( inside ) and on the chamber wall ( outside ) consistent round to round so the release of the projectile is very close.
Now what I think he's saying, but isn't getting across, is that with his load , one brand and type of primer shrinks his groups 60% when nothing else in his load is changed. That is entirely possible, because some primers don't work as well with some powders in some guns.
I have seen half moa reductions or increases between primer brands and types a few times in my own loads. Usually the differences are much less, but for instance, a couple of my 6.8 loads shot half moa better with CCI #41 than with the CCI #400, with the same powder charge ( load dropped 1 grain and worked back up ).