Jackie,
I have never read a thing about symmetrical vs. asymmetrical lacing on rear wheels as more or less desirable, although I've read comments on most everything else.
I have always built rear road wheels with the pulling spokes exiting from outside the flange, as that was how I was taught in 1970. Sometimes I will do the wheel symmetrical, sometimes asymmetrical. Hasn't seemed to matter to me or anyone else all these years?
My take on what really matters is high even spoke tension, good materials and the wheelbuilder's skill (and patience).
Chuck Brooks (have to go out into the shop and rebuild the rear wheel for the next door neighbor's 12 yr old son's BMX bike......lucky me!!!) Malta, NY