I never experienced any particular problem getting levers even just by sighting across them. Once that is done one merely rides for a bit to test the comfort and evenness. It's rather common knowledge that bodies are not symmetrical anyway. In my case it is more true, as due to an old soccer injury and a recent arthroplasty my left thumb is significantly different from the right. That plus my left arm being longer has resulted in my left lever being very slightly forward from the right.

There's absolutely nothing wrong with adopting a standard that gets things in the ballpark, but in the OP's case he was working with levers on a bare bar - no reason to not just test ride for the right feel after checking for a good start point.