The determination you mention (if it is the one I am thinking of) is specifically regarding B1 and inner-room bedrooms. The main point of the determination (There have been a few similar determinations btw) was that passing through a fire affected room, even with sprinklers, is simply not as safe as the code-compliant escape corridor/hallway. (I am not saying I agree or disagree with it, but that was the crux of the decision)
Here we are talking about the people who have to walk into the building when the fire has been going for some time and it is untenable for anybody else. Even fully kitted up, the firefighter is under a great deal of physical stress while in the heat. CLG and BDAG have done some published research into this. Something minimising the risk of flashover or even simply lowering the temperature of the room has got to be a great bonus for the firefighters.
I am sure any of the operational or ex-operational people here can explain how long a BA set lasts in good conditions and how long the same set lasts in severe heat. O2 uptake is a good indication of physical stress.
In fact, we could temporarily ignore B5 and simply ask one of the operational guys what they would prefer;
a) A walk up a stair with the high pressure hosereel with a sprinklered fire at the end of it.
or
b) A walk up the same stair, with a dry riser to connect to and an unsprinklered fire.