So when he says 75% brew house efficiency is he actually referring to mash efficiency? Is this the efficiency biab brewers usually refer to when they mention efficiency?
Brewhouse efficiency will equal mash efficiency if everything in the boil kettle gets dumped in the fermenter. For those who leave trub in the BK, brewhouse efficiency is less than mash efficiency. However, when it comes to packaged efficiency, it doesn't much matter if you leave the trub in the bottom of the BK or fermenter, you lose that volume either way. Comparing brewhouse efficiency without specifying the trub disposition is meaningless. Comparing mash efficiency or packaged efficiency is always unambiguous.
Since most brewers are interested in how well you/they did getting the sugars from the grain into the BK, comparing mash efficiency makes the most sense. What a brewer's trub losses are is much less interesting (usually.)
Brew on