Because... I have done it and...
when your life actually depends on a successfull emergecy ascent,
- controlled or not,
- buoyant or swimming,
you really, really want to have done it at least once before.
The resulting confidence and clarity of mind might save your life.
Freediving 25m horizontally is easy and freediving 50m horizontally is doable for anyone reasonably fit and relaxed with a little practice (well I did it many many times without being an athlete).
The limit here is the amount of oxygen in the blood (and also mental state: how well do you tolerate CO2?). Oxygen dictates how far you can dive without loosing consciousness (for me it was 65m untill passing out) and CO2 dictates how **** you will feel during the dive and when you will panic. Feeling bad is a mental hindrance only, though. OK, too little O2 or too much CO2 can both kill, but most likely it is the oxygen percentage that is relevant. 25m horizontally is easy, 25m vertically is even easier (given a SCUBA set).
When one dives at depth and breathes
high pressure oxygen then there is some extra O2 in the blood. That would be enough to maintain your consciousness from far greater depths that 25m (if normoxic air takes you 25-65m!). Breath hold also does not
feel that bad, because as you ascend and the air in your lungs expand, you can/must exhale and get rid of some CO2!
And hey, it's not a CESA, it is an EA.
I have done an emergency ascent only twice, once form 10mts and once from 20mts, but two things are certain:
1) emergency ascents are not controlled vs. uncontrolled - they just are; you want to get to the surface, no matter how. Style is not a factor here.
2) swimming or buoyant? Who the f cares? You want to reach air.