Daniel Sprong was waived then traded for. I don't think that is really a good explanation.
If a player is claimed on waivers, he hasn't cleared them, and if the acquiring team wants to send him down to AHL, they will have to put him on waivers again and he can be claimed by someone else.
But, if no one claims the player, he has cleared the waivers, and now can be sent down. It may be worth paying a late round pick for getting the player with his waivers cleared instead of claiming him for free but with the hassle.
Especially as if only one team claims the player on waivers and then put him on waivers themselves, if at this point no other team than his original one put a claim him, he will be considered to have cleared the waivers and the original team can now send him down.