There was a bay where the equipment was set up for anyone to test their loads. That was the day before WB started.
Some folks took advantage of the opportunity, some didn't.
It's impractical to check 150+ shooters ammo, at five rounds each, and still complete the match.
There is no more MDQ for scoring purposes so, once challenged and found lacking, it's a SDQ for any stage, after that, the ammo is used, and a MDQ for the second stage used.