RVDT: " I read it in a boooook".
I contest the described advice wholeheartedly. How many robinson/schweizer pilots have done ditching trials, I ask?
Secondly, I ask this: Why bother 'immediately' tempting fate by rolling the cab over as soon as possible. Why the rush? Because the moment you apply lateral cyclic, you are comitted to egressing the cab and inviting personal injury in so doing (which is why they warn you about it!!!!).
Sitting on the surface (of what could be a flat calm lake/river/sea might give you time to get your act together before the next inevitable scene wherein the cab sinks anyway. ANY time in addition to inverting the cockpit into cold dark water is better than an immediate rotating into the unknown.
In my humble experience I would NEVER advocate an immediate rotation, it, quite simply reduces your options.
Sbdorset: The RN and the RAF advocate a controlled exit from the aircraft before ditching thus minimising risk to human life for those who have left the a/c before the lone occupant taxi's well away from them and ditches controllably into the drink. It is an SOP.
Given the choice if you were sitting in the back of a helo and invited to jump 5 feet into the water with all your kit at the ready, OR stay inside with others around you and await a ditching and subsequent sinking with the associated mayhem.....what would you prefer?