The thing is, and this is is a truism but worth considering, fast (i.e. good?) runners can cover 5k so much quicker than slow runners. Some runners’ 5k ‘time on course’ might be well under 20 minutes, some closer to 1 hour. Either time could be an impressive achievement depending on that runner’s situation, their goals and what they have achieved before. And good nutrition will be different based on that ‘time on course’, which is going to vary with intensity; some runners might be working at threshold to cover 5k in 45 minutes, a huge effort and they should probably eat and drink accordingly. Easy to forget how slow we all were when we started.
The faster you can go, the harder you can go, because the finish line comes sooner (except that’s why the World Hour Record is so fascinating, because it doesn’t) so the event is shorter for you. By the same token, while riding a century sportive in 4 hours is really impressive, a rider completing the same century by pacing as well as they can for 8 hours has done a more epic ride IMO.
Anyway, on nutrition, I think we all agree it’s going to be individual. I’d hate for new TR users to think they’re doing it wrong if they aren’t shovelling in the carbs, or if they can’t get through a 1.5 hour workout just on water, or if they haven’t got special sports nutrition products. I remember when riding indoors for 90 MINUTES was a daunting achievement in itself, never mind intensity!