I admit I wasn't following along with Samsonov's situation at the time. But why would being drafted in one league limit his ability to play in another league if he never signed? Many players are drafted in both the CHL and the USHL for example and can choose which to sign with (or neither) - see Nick Malik.
Admittedly, this was 22 years ago. Rules have changed. Leagues have changed. Agreements have changed.
I believe it was more because he was underage and not NHL draft eligable. That is best guess on my part.
The point isn't what the rules were, it is that Ottawa released his rights to allow his signing with the Vipers. This shows a previous example of the 67s doing it.
With respect to NHL vs AHL vs Europe, we've seen NHL teams graduate players to the NHL prematurely because they don't want the player stagnating in Junior.
If Ottawa doesn't release his rights and the NHL team feels he will stagnate, they will keep him in the NHL or work out a Europe option if wither of those two options are deemed better for his development. So really it doesn't matter what Ottawa wants. This is why it is better for Ottawa to release him from his contract.