My Personal Answer: So a long long time ago Marc Merrill and Brandon Beck said in an interview that a big design guide for League was to keep changing things - a rotating meta. I am unsure if the design philosophy is the same, but that is usually what I think of when you see "Fair" champions receve buffs to land them in S tier.
Now I would prefer if - when this does happen - that champions dont see turbo nerfs to other parts of their kits as a result.
Thats very philosophical though and rides a lot into the mathematics of game theory.
The Correct Answer: Really, Jinx is a solid performer in the current meta, given that they are also changing Crit, there are expecting to see a hit to Jhin and Caitlyn specifically. Giving Jinx a placebo buff on the same patch might keep her competitive viableness, as shes more team fight focused than the other two. This is really similar to the Zyra buffs we have seen over the last few months