On the return I am connecting in HNL and don't even leave the airport, but the new itinerary shows a charge for the OGG/HNL baggage.

But as I say, having travelled many times with BA in Business and First, with other flights on my holiday being with the like of Qantas economy (completely different days to the BA flights) but the higher baggage allowance has always applied. I am just used to European rules I guess, the American ones seem as clear as mud. (especially as they weren't on the original itinerary and have just appeared with the 6th changed made by United)