The idea of the changes was likely made so that any buffs that are persistent and don't change would be in the left buff bar by the champion portrait so that they don't clutter unnecessary space in the center, while any buffs that contribute to the champ's playstyle are in the center buff bar.
The execution is that an overwhelmingly large number of buffs that are central to the champion's gameplay and should be in the center buff bar are on the left buff bar.
I don't know every single buff in the game, but I distinctly remember Nautilus' Titan's Wrath buff being on the left side. The reason I remember this is that I remember looking at the center buff bar to see the duration on Titan's Wrath, and I couldn't find it on the center buff bar. I knew I had it up because its visuals were still signalling that Nautilus has the shield. For some reason that buff was on the left and not the center. Buffs that directlyaffect the champ's gameplay need to be in the center for easy access.
Likewise, I remember some of the jungle buffs were on the left side. You kind of need those buffs in the center too.