The point isnt obvious here, since we're talking for the benefit of the guy who is wondering what size handlebars to get. I don't know whether all fit formulas are "good starting points" but it's true that this particular one will give you a number that will probably work ok, and it is probably less likely to cause problems than some of the other formulas. But it's misleading to bring it up when someone is asking for advice, and leave it at that.