DaveWC

None of the examples you listed sounded like advice, but rather habits of cyclists. And usually those kinds of habits aren't prefixed with "I intend to race in the near future and these are my habits to get there" but rather "I'm a hobbyist who enjoys cycling" or "I'm trying to maintain reasonable health & weight". And for those goals doing what works sounds reasonable.

As for the skittles/headache example, you're comparing that with cyclists describing their habits over years of cycling. If every time you have a headache over a number of years you eat skittles and the headache goes away then yes, I'd attribute it to the skittles & a sugar deficiency.