Ashe Q stacking patch 5.22

Ashe: " While Ranger's Focus is inactive, Ashe's basic attacks each grant her Focus for 4 seconds, stacking up to 5 times."

Caitlyn: "unenhanced basic attacks each generate a stack of Headshot"

I went into a custom and tested that Ashe doesn't gain Q stacks from the runaan bolts while Caitlyn gains stacks towards her headshot. The two descriptions both state that basic attacks generate stacks so I don't understand why runaan only stacks for Caitlyn but not Ashe.