I have seen players lose a ton of their game in far shorter periods of time then we are talking about. There are various reasons for it, sometimes people quit playing altogether, some people have health issues, some people simply lose the fire and simply stop caring.
And a person who quits totally, and then comes in and plays in a single event without having played serious pool in years, seriously what do you expect? Buddy Hall played as much as his health would allow, he never quit. Sigel lost a ton of his game since his prime, I have watched enough video of him from the 1980's and saw enough of his IPT playing to see that, yeah he still plays great, but he played ALOT better, ask Efren. Varner lost a heap of his game in his hiatus and is still getting back to his former speed.
Honestly, how much of their game do you think they need to lose to change things? How much worse is Chris Bartram shot for shot against Wu or Yang? A guy at Wu or Yang's level can drop to a Chris Bartram level, and suddenly they are not in the same league as Orcullo, but they obviously were. They would still seem to play great, but Donny, you seem to think that is the level they were always at, you are wrong, they lost a level or two and those levels are the difference between a Bartram and a SVB.