If you look at the measurements that JA does on preamps and power amps both SS and tube, there are usually differences between the channels. The SP Carver challenge is somewhat confusing. After the first round was over, SP declared Carver won. After that something happened and they claimed they could hear a difference between Carver's amp and the CJ Premier 4.
I think the real problem is that some people try to oversimplify the design, manufacturing, and testing of audio gear. According to one of our resident experts, everything you need to know about any audio component is contained in 4 measurements. The reality is that audio gear is built using components that all come with a tolerance attached. The more expensive the gear, the more you would like to think that the manufacturers are closely matching each resistor, capacitor, and transistor. In the case of gear built on circuit boards, the layout between channels may not be symmetrical which means the traces between the channels may not be equal. There is a reason that gear usually has differences in measurements from one channel to another. If you buy cheap gear that has great specs on paper, how much money do you think they are really spending on tight tolerance parts and then matching them?