I'm operating under the assumption that this is of value to the average young sedentary male computer geek I presume the HN crowd is largely composed of. Most people seem to be under the impression it requires hours of workouts and access to special equipment to see any results. The law of diminishing returns applies very strongly here, meaning you can see a significant portion of what's on the table with very little investment.
Using a soldier as reference was more intended to illustrate that doing the thing consistently every day is the important part, and is a major component of what the military forces onto its soldiers. You don't need a gym membership, you need a barrier to getting on with your day that shouts in your face "get down and give me $number", every, single, day, indefinitely.
So, your statement was actually "most soldiers look like guys who do a bunch of push-ups, so do a bunch of push-ups and you'll look like a soldier"? Hmm.
Sure, I get that most soldiers don't technically look like Rambo, but if you weren't using that phrase as a figure of speech to convey "extremely fit", then it's kind of meaningless right? Like saying a "professional boxer's physique", then saying you were thinking of Butterbean.
So, yes, if we lower the bar to say "slightly above average", then your point is "more valid" though a good bit less revelatory. You're essentially saying "exercise will help you", which I think we can all agree on.
But, the broader point you're now making that doing anything is much better than doing nothing is certainly valid and worth emphasizing--especially for us in the HN crowd.