I doubt the professional reviewers received a "special" gun, but I'd be willing to bet they at least got one that test fired "well" off the rack. Had they received one straight out of the box that shot like the one I got, the reviews would have been much different. After 2 weeks in the shop getting all of the barrel supports and pellet probe carrier aligned, and a new barrel, mine now shoots as advertised, "1/2" groups at 50 yds. are typical". Not everyone has the resources or knowledge to "fix" one of these new PCP's, and they shouldn't have to considering the cost. The good news is, if you do get a "bad" one out of the box, it can be corrected, one way or another.
As the tech advances in these guns I think we should start to make a distinction between "tuning" and "adjusting", because simply making a change to built in adjusting device to affect velocity really isn't tuning, its just a purpose built mechanism designed to acquire the best possible performance from a given pellet and gun/barrel combination. Tuning is doing some type of substantial work; correcting mechanical character flaws or design issues, changing and modifying springs, and components to improve the performance of a weapon are some of the things that fall into the category of "tuning". The Impact's external user adjustments allow for a wide range of velocity manipulation, wide enough to accommodate about any available projectile weight in 4 calibers, and an arrow launcher, but I don't think 1 click on the power wheel and 1/4 turn on the hammer spring qualify as "tuning".
The Impact is a remarkably accurate gun by the way, when it functions as intended.
