The underlying thought goes something like this:gurumasta:
...Lets assume you make a dive plan. Lets assume you follow the dive plan. In that dive plan you plan to begin your ascent with sufficient gas to ensure you can ascend safely, with an appropriate amount of gas remaining in case some unforeseen event occurs. Lets assume, moreover, that you track elapsed time; your gas consumption; and that of your dive buddy. With all those assumptions as a foundation, you will never suddenly realize that you're out of gas to begin with. (You would recognize that you have "issues" before the situation gets to the point of an emergency...) These assumptions provide actual security, instead of false security. The implication is that the only divers who might need a pony bottle, to suddenly turn to in an "aw crap" moment, are those divers who either don't have a plan, aren't following a plan, aren't paying attention to things like time or gas consumption, don't have a buddy or have gotten separated from their buddy, and are basically underwater Opie's who are accidents waiting to happen. In this case pony bottles may not solve the total situation the diver faces. Hence, a "false sense of security"...assuming the diver doesn't do anything else properly to begin with.
(Of course, life is rarely so black or white. Many other issues can be brought to the dialog, including care and feeding of buddies, solo diving, traveling to exotic destinations as a single diver, deep diving, water and rust particles inside rental scuba tanks, and loads of other anecdotal scrotum-trivia. But I think you get the idea.)
Does this make more sense to you?
