I think if they were ashamed of their past then they wouldn't have performed Lets Get Ready to Rhumble on Saturday night. I also remember them peforming it on CD:UK one time. When they did Jonathon Ross the other week he also showed one of their other videos and took the piss out of it.
Buying up the rights to their old shows so they can control when they are shown isn't unique to them as I know of at least one other celebrity who has done the same, though I'd question whether or not its true in A&D's case because I've seen clips of Byker Grove and the Ant and Dec show ( where they shaved that girls hair off) on various nostalgia shows over the years.
What happened was they went through phases - and it may well have had something to do with who was influencing them. There was a long period where they wouldnt let anything out - maybe they felt some of it was poor or it was just getting boring people pulling the footage out every time they got interviewed on a talk show, but other than the Byker paintball clip, and certainly not the music - very little was shown. They seemed to open up a bit with the clips a couple of years ago, and since Gallowgate was aquired by James Grant and they now have less to do with the actual release of stuff it seems that anything goes. Maybe they have matured a bit and gotten over it but there was definitely a phase where they were very serious over the control aspect, but as you say, there are others that do the same thing.
They are great guys, but the idea its all natural is wrong - they are compared to Morcambe and Wise a lot but M&W were naturally funny. Ant and Dec are given all their jokes and told what to say, they arent funny without the script or at least being told how to act. But then again, i could name a lot of other presenters the same.