Tbh I've lived already through at least three different dogmas contradicting each other. Those are sometimes behaving like a fashion

I would say that dogmas are normally born out of necessity before they become dogmatic, so it is beneficial to analyze and extract core values out of dogmas instead of entirely ignoring them. In this particular case we can conclude that the threshold should be determined per team, because some team may have a member whose working memory is exceptionally smaller than the average. (Ultimately this shouldn't surprise anyone because the coding convention has to be per team anyway.)