I don't know anyone who loves cooking who would not want to try different ways of producing a sauce. But let's not forget that cooking is also chemistry, and as we all know, the combination of certain ingredients in different proportions will give different results, just as will the use of slightly different ingredients (i.e. butter/cream/milk ) whose chemical structure is non the less different will produce foreseeable results that can be measured
as chemical analysis. 'Jus' comes into the equation because it's the butter that's the thickener, without flour or eggs - or at least that's what I learned at cookery school. Chemical reactions can be predicted and measured. My DH studied chemistry at University, and he's helped me many times when it comes to making sauces that don't split. So I would say that conventional wisdom shouldn't be ignored, because there is a basis of fact to be taken into account.