Mark, It seems to me that the ruler trick is handy when restoring a vintage blade that you don't want to spend an hour flattening, but not useful otherwise. A L-N blade should be already flat, so the ruler trick gives no benefit, and once done requires you to use it from then on. I don't have a chisel plane but have plenty of other L-N planes, and I've never needed to spend any meaningful time flattening the back on any.
I guess my answer is redundant with Freddy's, but two opinions are better than just one, hey?
Mark Maleski