Is the cooldown on Throw Voice shout bugged?

Throw Voice is unique in that there's no benefit to a higher magnitude power of the effect. The enemies are distracted, and investigating somewhere, or they simply aren't. It's a binary either/or scenario.

So, Bethesda had to find some other benefit to the 2nd and 3rd words - there was no magnitude or duration to increase like most other shouts. Their response? Lower the cooldown.

So while there's never any reason not to use the level 3 shout, it still requires 3 dragon souls to reach that point, and given that you learn all 3 words of the shout simultaneously (unique among non-unlocked shouts like Dragonrend or Clear Skies), it's not inconceivable that you may need to go dragon hunting before you can use the level 3 shout.

So to definitively answer your question: no. In all likelyhood, the recharge times are in the correct order, even though this is relatively unique among the shouts. (For another example, see Call of Valor, which has identical recharge times throughout all 3 levels).