Why do we learn all three words at once?
Why are all the words identical apart from cooldown?

This seems incredibly.. odd. Seems a waste of two perfectly good shouts. Why would you ever use only 1 word of the shout? or even 2?

Because you didn't have the Dragon Souls to unlock all three at once.

And that's about the only reason not to.

It's a pretty weak and specialized shout, hence why it all came in one piece.

It is pretty worthless, you can just use an arrow instead of the shout, unless you're lazy.

You make a good point, but I think it's because a full shout is made of three words. Would it not be odd to have this one shout with only one word? I also think it is all located at one spot because the three words do not differ so much as to have 3 different locations for the 3 words.

Throw voice is a favorite of mine, I use it to lure enemies into traps in dungeons. The spike doors are my fav.

You have to hold down the shout button for longer while you're sneaking and the whole reason of this shout is that people are looking for you so the longer you hold the shout button, a second longer they could be looking for you.