Thanks for the detailed description of that time trial.
Do you agree that, at least once a swimmer has developed a reasonably efficient stroke, swimming under physiological and mental stress causes adaptations that enable swimmers to swim more efficiently under similar conditions of physiological and mental stress? Or are you making a different point?
I take it your thinking has evolved from the old "never practice struggle" maxim to the statement in your post that there is "the potential to gain value -- even enjoyment -- from struggle." (Or so at least for swimmers at some stage of the learning process.)
In my experience, I find a close correlation between swimming-specific fitness and technical efficiency, and vice-versa. Technical breakdown wastes physiological capability; poor fitness degrades the ability to sustain technique. Each promotes the other. I think one learns things in a fatigued state that cannot be learned at all in a non-fatigued state, because the necessary conditions are not present -- mental focus and control at the top of the list, for example, the ability to perceive unnecessary strain and drag sources and replace them with more efficient movement patterns on the fly and sustaining velocity while reducing energy costs. (A different skill, mentally and physiologically, than just bludgeoning through and hoping to survive the stress.)
Thanks again for the post!