You are talking about moving established players after they have broken out who are being moved because they wanted out, that was not really what the discussion was about.
The position was that holding the prospects longer to see what you have before moving them will often produce more over-all value to the team than moving several of them before any of them breakout.
The sum value of moving a bunch of unproven prospects often does not add up to the value of holding them longer and identifying the best of the lot to keep, even if this means losing value on most of the ones you will move on from.
There are exceptions, some prospects are worth a ton. But in general, we were talking about 3rd and 5th round selections. These kids have very little value, so the opportunity cost of holding on to them vs trading them for a return is minimal.
In the Sabres case, the glut is with small forwards, which historically have little value until they have consistently produced in the NHL. As prospects, rosen, Savoie, Ostlund etc (and even peterka) are not going to return equal value alone. A package of them along with draft capital will be required to bring in a youngish effective player with term.
Your examples ignored the production and value Sam and Jack provided while Sabres, and those two situations are also very unique in that the players asked for trades, so I think we are talking about different scenarios here.