You're examples are mostly pure speculation. Mcadoo would not have been a top 5 pick, those were just rumors from months before the draft, Henson was not even close to a top 10 pick after his freshman year (that one is just hilariously wrong), and Ed Davis is also just predraft speculation. Barnes I will give you, he probably should have gone.
The idea that Roy lies to his players to get them to stay is laughably false. He usually does a great job of getting them accurate information on their pro prospects to make an informed decision, he just recruits players who are willing to stay 2 or 3 seasons if they have a shot at a title.
Whatever you have to tell yourself...the top 10 of the NBA draft is typically very similar to what ends up in mock drafts, much easier to predict than the NFL draft. So all these sites that do this every year and are relatively accurate on the picks is PURE speculation?
Recruits guys that are willing to stay 2 or 3 seasons? In recent history the top 5 guys in almost every recruiting class are 1 and done. Look at the most recent recuriting classes:
2011: McAdoo is the only one in the top 8 of that class who has not gone pro yet.
2010: Of the top 8, Barnes, Sullinger, and Terrance Ross were only ones not to be one and done. Ross made a bad decision, likely costing him around 10 spots in the draft. Sullinger as well, even with his less than desired size, he still would have been a top 10 pick in that weak draft if he had gone. He ended up going 21st in 2012.
2009: Of the top 8, Henson and Renardo Sidney(was terrible) were the only ones who weren't one and dones.
2008:Of the top 10(Davis was 10), only Davis, Samardo Samuels(terrible player, now playing in Jamaica), Scotty Hopson(now playing in Israel), Devin Ebanks(bench warmer for Lakers) were the only ones that didn't go pro after frosh season.
Fact of the matter is that the trend is there. Roy somehow convinces these one and done calibre, top 10 players that staying in school is somehow better for them. As an obvious Duke fan, I actually thought all of those players coming into school had allstar NBA potential. It seems as though their growth was stunted by staying in school.