The metal removed would not come from the "side" or the machined face of the rotor. That will shorten the service life of the rotor.
Also, rotors have so much less mass on the outer edges as compared to drums, it is almost not worth the effort to "balance" the rotors. It would be like checking the tongue weight before every trip after the unit is all packed. Sure it will be different, and moving packed items around in the trailer to achieve a 8% tongue weight every trip is not going to make that much difference.
Those clips seen on the inside of rotor fins also have another purpose besides balancing. To reduce/eliminate brake noise. The rotor can vibrate and create a noise under certain conditions. Like taking a wet finger and moving your finger around the edge of a wine glass. Under certain conditions a noise will occur.
1966 Mercury Park Lane 4 DR Breezeway 410 4V, C-6, 2.80 - Streamless.
1966 Lincoln 4 door Convertible 462 4V 1971 Ford LTD Convertible 429 4V Phoenix ~ Yeah it's hot however it's a dry heat!