Muffler has a hole

[H3 Hummer]

I noticed something dripping from underneath my H3 - it was quite dirty so I took a closer look. The drip was coming from the muffler - it is most likely condensation dripping through a hole.
I already had an appointment scheduled for next Tuesday for my oil etc. so I called them and told them. The Service Advisor told me that is normal - I said in the middle of the muffler? He said yes.

I know it is an actual hole because I can slightly feel the air coming through - what I don't know is it made to do this like he said? Upon closer review it looks like it is supposed to be there.

The area is right before the leaf springs - the muffler is expanded in this area.