Meditation, like exercise, can be a lot of things.
Choosing a brief walk can be exercise, or a brisk walk that's a little longer - maybe doing some forms of housework can be exercise. But exercise can also be running marathons, swimming laps, playing street hockey, dancing in your kitchen, skateboarding or messing around on the monkey bars. Those would all make you feel your body in various ways, both during and after the fact.
I do think your empty mind train rides can be meditation. The fact that much more intense or demanding forms of practice exists does not invalidate that.
(To belabour the metaphor a bit, regarding potential dangers - if somebody has a knee injury, some forms of exercise will be safer for them than others. Take care of yourself!)
If someone wrote about how taking a twenty minute walk in nature made them more productive, I don't think anyone would reply 'I swear every day I see a "new" fad targeted at fixing one's mood and every time they're doing so much mental gymnastics to not use the word "exercise."'
Who cares if they're doing exercise or not? The person who takes walks presumably knows it's a form of exercise. They're not talking about the other forms, they may not be able to do Crossfit or go skiing, and they might not feel confident expressing opinions about the entirety of all exercise, but they definitely know that walking works for them.
Yeah, I think that's probably correct.
I do somewhat see the value in promoting specific, accessible meditative practices without necessarily using the word meditation for it, simply because it can be needlessly intimidating and put some people off because they come carrying a number of assumptions.
Maybe that same principle does also apply to exercise - some people will do it by accident and have a good time, but still balk at idea of doing capital E Exercise as a distinct activity in itself. Sometimes it really is just a mindset thing.