For 70, all cars got the single driver's side chrome mirror as standard equipment. If you wanted dual mirrors, you ordered RPO-D35 and got dual bullet mirrors.
72 was different according to the option list. The chrome mirror appears to still be standard, but RPO-D35 says "remote left hand mirror" instead of "mirrors sport right and left hand remote" like 1970. But, the option book says right hand sport mirror also available. http://www.nastyz28.com/camaro/1972/72b-14.jpg
From my understanding, the chrome mirror was still standard as mentioned.
If you ordered the 'remote mirror' option, the chrome mirror was replaced with the optional bullet mirror with remote cables. But still only on the driver's side.
If you ordered a passenger side mirror, it was included with the car to the dealership, and the dealership drilled and installed the pass. side mirror.
I have the build sheet for my 71, and it calls for left remote mirror. My car never had a mirror on the pass. side door.
I'd be willing to bet that since the pass. side bullet mirror was dealer installed, that if a car came in with the standard chrome mirror, the dealer would install a pass. side chrome mirror upon request/$$.
I believe this was the case for the first few years of the 2nd gens. Later I think the bullet was standard, and finally the pass. side was as well.