I feel TUT does play a role, not the only role, but another piece of the puzzle in training. Understand, I am coming from the powerlifter standpoint as it is what I am.
The reason that powerlifters train in low reps is not for maximum hypertrophy, but for maximum central nervous systemm recruitment. It is a different type of muscular growth. The density of the fibers get thicker where in bodybuilding, TUT is responsible for more sarcoplasmic (cell stuff) growth. The sarcoplasmic growth does make you bigger, but not neccessarily stronger, where the fibers getting thicker leads to more strength.
I have always felt, like yourself that TUT does play a role. This is why it would seem that madcows 5x5 training works so well. It allows enough time under tension to enocourage sarcoplasmic growth, but also allows a high enough weight to encourage myofibral growth and more strength.
When the object is to get stronger, there are actually 3 specific ways to do this. Check out Vladimir Zatsiorksky's "The Science and Practice of Strength Training" for more stuff on this:
1. Get faster. Increasing force production with a submaximal weight will get you stronger.
2. More CNS firing and an increase of muscle recruitment. Basically, it training your cns to fire all your fibers at one time.
3. Hypertrophy. You do a set, Like shadow was talking about earlier, take a short rest and do another set. This allows for more muscular recruitment of typeI and type II fibers..(I won't get into different subclasses of fibers).
On a side note, I have never seen a powerlifter without a lot of muscle mass. The only reason that they may not is they don't want to, so they can stay in their same weight class.
I guess I only wanted to show another side of the TUT debate. Strong does not mean mean big, but big does not equal strong. Basically, you have to decide what it is that you want to do. IF you are a sprinter, you have to look at different strengths like starting-strength, speed-strength, acceleration, strength-endurance and a host of other.....I don't necessarily feel that it is only TUT that contributes to their muscluar physique.
The energy systems also have to be looked at. If you are looking at the marathon runner/sprinter example again......a marathon runner uses the o2/lactic acid system of regenerating atp and also muscle mass is decreased due to the body needed to breakdown protein in the body for carbs (prot can be broken down into carbs btw) and also the body forming to the requirements that the body is put under. It is not optimal for a marathon runner to have a lot of muscle mass.
Weight training and sprinting utilize the gylcogen and creatine phosphate energy system predominantly (all energy systems are utilized in some way or another and to different degrees.)
Shadow, I agree that TUT does play an important role, but I would argue that it is just another part in the equation of strength and size.