You don't see those stages in matches very often these days. Its not expected that the shooter will make a first round hit on those stages. Quite the opposite. They are meant to test the shooter's ability to spot their shots and correct, which is a core skill even in the known distance matches most PRS matches are. UKD with unknown size or range-of-size targets were more common in US matches before the PRS was formed and were used to demonstrate the folly of thinking in linear units (inches or cm) instead of using the reticle. You can only really do them in a field match where you can keep the shooters from ranging the targets while others shoot or from communicating with each other. Limited places where you can do that, and its not feasible with the large number of shooters in many of the matches you see these days.
There is a PRS match that will have UKD targets in the fall in Kentucky:
https://www.facebook.com/PracticalPrecisionRifleChallenge/
The MD is a recently retired SOF sniper. The match is limited to 80 shooters to be able to do it right.
Not sure if he will have unknown target size, but I would expect him to have things like targets on sticks out in the open where the over-reliance people have on LRFs will cost them points when they don't get readings or pick up things way in back of the target instead of the target itself, or time out trying to transition back and forth between the rifle and the LRF. Sometimes the reticle just is the better tool for the situation...
More often than not, you'll just be using the reticle instead of the turrets or in conjunction with them. I just got back from the K&M Kahles PRS match. They had a stage where we had to shoot 5 targets between 700 and 1200 yards in 60 seconds. Only one shot on each, and after your first shot you got DQ'd if you touched your scope again. Quite a few guys cleaned the stage... kinda required a reticle. Many stage required transitioning between different distance in a very short time that would not allow for turret adjustments.
