You're not mistaken. The point and purpose of polishing is to reduce aerodynamic drag and turbulence. This is good for exhaust, and bad for intakes. The reason it's bad is that turbulence is NEEDED on the intake side to assist with atomizing the fuel. If there is no turbulence, the gas may not burn well in the combustion chamber. It's much harder to un-f**k it after you bolt it back on and your car runs like crap. Porting IS okay on intakes, though. Only polish exhaust stuff.

If you want to polish the outside of it to learn how to do that... you couldn't have picked a more difficult part. You'll be a pro at it by the time it's finished.