It depends.
When I have an order for a bilateral study (or sometimes "4 limb"), I interpret that as giving me free reign to perform what they ordered. I have done a 4 limb EMG once or twice in my career (I am well over 10K studies)
Like today, I had an order for B UE for CTS. The patient only had sx in the L arm. I did the L arm first, it was normal. I stopped the study and wrote "the RUE was not tested in light of the normal study of the LUE and all symptoms were L sided".
If the L arm showed Severe CTS, or an acute radiculopathy, then i likely would have checked the RUE. If the L arm showed MILD CTS, I probably would have stopped.
Understand?