A couple of factors can influence the ability of a muscle to generate force without directly contributing to an increase in pCSA.
More force can be generated when more motor units are activated. FT motor units generate more force than ST motor units because each FT unit has more muscle fibers than a ST unit.
The length of a muscle. A longer muscle, as measured from origin to insertion, will have greater elastic properties, resulting in more energy stored, then released.
On the other hand, sarcoplasmic hypertrophy occurs with an accumulation of intercellular fluid and non contractile proteins, which do not influence muscle force production. This is fine for a BB, but terrible for a PL/OL.
Gladiola, when Hannibal and myself, as well as other power and Olympic-style weightlifters are training, we are not just training to increase muscle size. That is a side effect of training, not the purpose. Or rather, it is not the main goal. Other things are equally, if not far more important.
Training the CNS. This is done via the maximal effort method. This involves lifting a maximal or near maximal weight in either a competition lift or a lift designed to closely simulate/stimulate a competition lift. This improves motor unit recruitment, rate coding, and other factors that are not stimulated training with a lighter weight. This sort of training does not generally contribute to hypertrophy when compared to higher rep training.
Improving the skill of a particular lift. This is done via the dynamic effort method. It involves lifting a light weight as quickly as possible. This is done for a low number of reps (2-3), but a high number of sets (8-10). This not only improves the skill in the lift, but also trains the stretch reflex, allowing one to become more explosive over time, if done correctly and carefully. As the time under tension is still relatively low compared to many BB programs, this method is not as conducive to hypertrophy, but will produce more size than the maximal effort method.
As to why the lack of eccentric work, it causes more trauma to the muscle itself, which requires more time spent resting and less time spent training. While a muscle may be stronger during the eccentric portion of the lift, we are training to improve the concentric, and this is better served through other methods. The more time we can spend improving sport specific skill, the better, and this is not the case if one is spend three or four days limping around following a squat workout.
Here is a good article on conditioning:
http://www.elitefts.com/documents/gpp.htm