I think you misunderstood my point. It was a reply to Jokar's concern regarding water damage from a sprinkler system and basically comparing the two, intended in a similar vein to what you said, but more of an emphasis on not refusing to install a sprinkler system because of the possiblity of water damage.
Regarding the actual provision of a sprinkler system in the regard that this topic is discussing; It will be to ensure the life safety of other people in the building. The FRS involved will not have been challenging anything for property protection. (Even with this particular expert witness' help.)
If we have a fire in a room where it is sprinkler controlled, it is much less likely to make it out of that room. Even if the smoke makes it out, it should be reasonably cool, and unless you are sleeping in a HMO with all the doors to the stair open, thus allowing smoke into your room, the system should be enough to guarantee your life as far as is possible. (If you decide to sleep with all the doors open then you would probably live slightly longer with a sprinkler system installed but the end result would be similar although with less charring.)
Disclaimer: I am not saying that all single stair flats require sprinkler systems, or that statistics justify it, just pointing out where it would help.