I also suspect that thinking of bar height in relation to saddle height may be the wrong anyway. It makes sense to set the bars at whatever height feels best going down, when I’m stood up anyway, so saddle height is irrelevant.
Damn good point, a lot of the rules of thumb, or obsession even, with fit is a hangover from road biking, and isn’t really applicable for a trail bike optimised for the alongs and downs. As long as you can get it uphill in safety and sensible comfort, it’s the down, with the saddle out of the way, that matters.
Even on non-fireroad XC this is true I think, roadies spend hours in a single position, on any mountain bike ride, we’re all over the bike.
some thoughts on this here: http://www.bikemag.com/gear/bike-exclusive-konas-2014-process-line/