Why does QSS remove Teemo's blind

Blinds are CC.

Teemo's E is an on-hit effect while Cho'gath's E casts a spell on each basic attack.

Blinds are a CC

It is CC.

Blind is considered a disable.

Teemo's E is an on-hit effect, not an ability. Every auto attack he fires has that effect on it. Cho's E is an ability, not an on-hit effect. Every time he attacks while the ability is toggled on, it will trigger.