Well, the only way to find out is to cut the exhaust open and see how they routed the piping/baffling.
Logically thinking, everything is already baffled and piped accordingly.
Here is an example of an OEM muffler from a Honda S2000:
Here is how it looks like from the inside (ignore the diagram, I grabbed this off Google and is not mine, only used as a visual reference):
I would imagine it's probably pretty similar except instead of using a 1-2 Y pipe (like this example here), it's a 1 to 1 pipe (for whatever engineering reasons), and they would extend the piping out the back of the muffler housing.
Being that the majority of the sound has already deafened, a small resonator is only needed to achieve a similar performance or decibel level. I would think that using a straight pipe would just... be a straight pipe and completely change how the exhaust flows and how the vehicle sounds.
It could be that it may not even be as baffled within the muffler, as in it's just a big open canister with free flowing exhaust. One portion in the muffler with sound deadening/baffling, and the "extended piping" taking the rest of the flow. With the additional length, and resonator at the end, may be enough to tame the sound and flow of performance.
All speculation and hypothesizing without cutting open the muffler, of course.
Although I am not an engineering expert, nor am I a multi-billionaire conglomerate business owner, I would think that a lot of science, money, and time went into why it looks and performs the way it does.
I hope this helps.