I'd even put it differently; regardless of how long rescue may take to arrive, the LJ may make the difference between you being able to make use of the rest of your SE, and not - and hence survival or not. My link expands on that thought.
Your point about hypothermia is spot on, of course, and for those reading this who haven't seen it before, this chart from the
CAA Safety Sense Leaflet on Ditching is worth studying:
Note that in UK winter temperatures
cold shock can kill you in under an hour - before the onset of hypothermia - if you are not protected in some way (such as immersion suit/out of the water etc).