Well the problem with opening that logic is that there's many other fruits that would need a 121 tier then, even among Paramecias/Logias.
Pika/Goro 121 speed tier for example.
Diamond fruit 121 durability tier.
Jesus' muscle fruit 121 strength tier.
Etc..
The point is seen, but Personally don't see the need in a 121 speed tier in general anyway
If +3 durability ranks means what I think it does, more or less gets you to +121 or a tier higher than that in durability once your base durability at 101 right? Would be even higher with 120 in dura
I mean, it would make sense for Jesus' fruit to get to get the user to that point... But it's really up to y'all. That's was just my opinion lol.
Kallavan can still get the dura boost with the dragon via a defense point can't he? So it ain't really a big deal imo