The analogy is not good because cardio training, core strengthening, and stretching are trivial matters. I can give a very vague description of what I did and what I was trying to get out of it and you can think of a number of things that I could have done.
But in point of fact, I ran two miles, balanced on my butt with my legs raised and hugged my knees then extended my legs 100 times without letting my feet touch the floor, then I sat up, spread my legs as wide as is comfortable, and gently bent towards my left foot, focusing on keeping my back straight and lengthened. I held that pose for abotu two minutes then switched to my right leg.
Now imagine I were to make claims that my particular pattern of exercise was the only real way to attain cardio vascular health, core strength, and limber leg muscles, and that you could NOT, in fact, attain this instruction at most gyms. But I and the people who trained with me would never actually supply a paragraph like the one above this one, just thread after thread about how awesome the cardio, core strength, and flexibility benefits are.
And any good running coach will tell you that "running two miles" tells one very little about what you actually did or did not do during that run - and that's a relatively simple conventional exercise. Just as "I did shiho-nage" tells me very little about what you're actually doing or not doing without a common frame of reference.
Nobody that I know has ever claimed that what we're doing is the only way to do anything - Dan has said that specifically on Aikiweb many times, and people in this very thread have given real world examples of other people doing the same or similar things.