Manaflow Band on Tahm Kench (Bug?)

I've been playing tahm kench with arcane comet and w max in support and spitting minions at enemy laners for decent poke damage. it gives tahm something to do in lane against ranged supports other than wait for the enemy to make a mistake or cc your adc.

The main issue with this is that, if you take manaflow band, it does not proc off of tahm's minion regurgitation when hitting enemy champion. This leaves tongue lash as tahm kench's only semi-reliable way to stack mana flow band. And, like I said, that is semi-reliable at best when compared to the aoe minion regurgitate. Is this intended? By manaflow band's decription, i don't think it is.