"Ahri's charm does not interrupt dashes anymore"

Counterplay. For the quick, if you see Ahri's charm coming, if you have a dash, you can dash away without being caught mid dash and cancelled. Like imagine Ekko vs Ahri, she charms, Ekko tries to react and dashes away but gets caught mid dash, forcing his only escape to be wasted. Now it gives a little wiggle room to kind of maybe get farther away. Why this doesn't apply to other CCs is both thematic and kit related. Thematic because charm is, well charm, in that it entices you to come to her, but wouldn't make sense if you could somehow stop mid dash and suddenly go to her. Logically, you'd finish your step, then turn and walk unlike a stun where you are forced to stop, not because you "Want" to as in charm's idea. Also, she has a triple dash ult and an MS boost. The idea is that she can already easily get you, so it's a way to cut back that chase power just a tiny bit. But, overall you won't ever notice this.

rito had a great need of making it impossible for ahri to lane against leblanc and diana

I think it was good that it can stop things like dashes. Rewarding you for hitting your charm. Why is veig's cage the only thing now that gets to keep it? It doesn't even need to stun you to be effective, just being inside the damn thing is basically a "stun".