Its not a glitch, PD simply put the exhaust line as straight as possible.
Here's a picture of a GTR exhaust normally found:
Removing the "T" would give the exhaust gases better flow.
They may have base the design on the NISMO GTR RC one
That's all fine, it's more the textures around the exhaust. They're clearly ment for a grey car, and these is no "transition" between the textures even when you have a grey car. I'll try to post a pic later to show it.