@RIOT Is loot from levelup rewards determined just like hextech chests?

I know it's kind of a silly question, but are level-up rewards determined when you open the capsule, or when you obtain the capsule? I know that hextech chests determine their loot when you open them, not when you purchase or earn them. I just wanted to make sure champion capsules function the same way. I know it stands to logic that they would work the same way, but I wanted to make sure. I've seen less logical design decisions before.

Because, as a frequent support player, I am pretty hype about Pyke, and I want to get him with a Champion Shard if possible. 7300 or whatever a newly released champion costs is a lot of BE, and I'd kind of like to avoid paying that much if possible. So I wanted to know if saving my level-up capsules would make a difference or I should just grind arams after Pyke is released.