Having a time in mind, like having a distance/depth to reach, is a "fundamental" mistake because it throws the static to dynamic phase out of balance. A preoccupation with time means that divers learn very little about sensing their way through the dive, a much more reliable indicator. More often than not, the experienced diver prolongs the static phase at the expense of the dynamic phase, by overriding contractions. This means that he/she overreaches, possibly beyond the 'point of of no return'. There are many ways to fool the body into thinking that the urge to breathe has not been reached before swimming off, e.g., counting, looking at the watch, swallowing, etc.
On the other hand, with novices there is a tendency to cut short the static phase (mental overload) and aim to swim far, e.g., "must get to the wall" or a constant looking for the wall. If suffient time hasn't elapsed blood flow to the muscles will be kept patent resulting in a rapid, out of control desaturation of O2 and blackout, that is, if the diver continues beyond the sensation to surface.
When that youg fella from your club had a BO he did made two fundamental mistakes: he went through several, possibly many, contractions in the static phase, indicated by the prolonged duration compared to everyone else, and secondly, looking for the wall as a goal to reach on numerous occasions. It is possible that he could of been excessively warm, which would of delayed the contractions to much later but I think it is unlikely considering his low body fat and the quite cool temperature of the water (~27 degrees + shade).
Signs of possible lung squeeze: mild pressure on the chest....quite noticeable.
Most bleeds involve reverse packing under already elevated -ve chest pressures. All this does is put excessive pulling pressure on both sides of the closed glottis.
Some preliminary results on experiments we've been carrying out here on the east coast: exhale dives resulted in significantly more elevated end-dive O2 tensions than with inhale dives.
Though the results should be taken with some caution, as they were obtained from my particular case, they do indicate the potential merit of the strategy considering the observations many of us have noticed in the clinics, i.e., that most divers achieved similar results with inhale and exhale after just two days parctice. Of course, I'm not referring to doing static breath-holds, but actual dives.