It's interesting.
From a player development perspective it's probably pretty scary to bring in a 25 year old, essentially a AAA type of prospect, and guarantee him a significant sum of money without being able to demote him. What if the player has trouble adjusting and gets in a rut? What if they actually do need to work on something in AAA? Not being able to freely option them for their own benefit actually increases the bust risk, as far as I see it.
On the surface it seems like a small thing but I can see why Toronto didn't want to write it into the deal. Maybe it also says something about the player... like, the team is going to guarantee you 30-40M - you really don't want to accept the possibility that you might need to work on something in AAA at some point?