I too have never seen a 98% singles shooter on the 20 yard line, so I did some checking. I have the 2008 Average book in Excel format that Neil supplied me. According to those records, there were 31653 shooters who registered at least some ATA targets last year. Of those, 93 had singles averages of at least 98% and handicap yardages of 20.5 yards or less, less than 0.3% of all ATA shooters. Of those, only 39 shot any handicap targets at all, so we're really only talking about 0.1% of all ATA shooters. Only 16 of those shot more than 100 handicap targets (0.05% of all ATA shooters), with the maximum number of handicap targets shot being 800 (800 singles shot with average 99.38%, 800 handicap with average 90.25% and 20 yards shown, 600 doubles with average 95.67%). This shooter, by the way, was foreign - I'm guessing Australian by the city name, but that's only a guess. Also by the way, none of these 39 shooters who shot handicap were from Kentucky. The ONLY possible anomaly I see in the data is the one shooter, from Missouri, who had a 98.67% average on 600 singles targets, a 99.00% average on 100 handicap targets, and yardage of 20.5. I could expect him, based on the rules, to be at least at 21 yards, but I suppose he could have been a subjunior who got punched 1.5 yards from the 19 for his 99. Looking at him in the ATA database in the 3S software does show he just turned 16 within the past week, so that is a plausible explanation.
In conclusion, almost all of these 98%+ singles shooters at 20 yards shot very few singles targets (900 at most, and then only in one case), and almost no handicap targets (100 or less in 80%+ of those shooters).