Some guy down under decided that true BIAB implied no sparging. Fine, but I like either rinsing the bag with hot water or "dunking" the bag in a volume of 170 F, pH-adjusted water for 10 minutes -- basically an extended "mash-out" of sorts. Yes, I now have an extra vessel to clean but on the small scale of my brewing, this is not a big deal. Interestingly, my OGs have improved a couple points since going to the dunk method and I usually overshoot Qbrew's estimate. I should also note that I have never brewed with a mash tun, Vorlaufed, or been to Munich so I'm still working on getting that clearer pre-boil wort that Palmer has us all striving for.
And then there are aspects of thick-mashing vs full volume BIAB thin-mashing, and hop utilization calculations that come into play. I put these considerations in my "needs review when I have the time" category.
As for step-mashing, I agree that it does produce a highly fermentable wort and I do like the idea of breaking down long-chain proteins to help mitigate haze. It is nice to be able to step-mash with BIAB.
Some day maybe you will find me out in the garage boiling a 5-gallon batch after mashing in my Igloo cooler, but for now -- or until my wife kicks me out the kitchen -- I'll stick with mash-in-sack!🍻