Exactly, a "step" on a 10 mike hike is no better than a "step" going from the sofa to the TV. It's still a movement. That's what matters. Moving the muscles, improving blood circulation, etc.
Of course, a 10 mile hike will raise your heart beat to a much higher level than walking from lounge to kitchen, and it's said that best exercise is to get yourself slightly breathless which is apparently optimum to get the heart and body moving.
But, a step is still a step and better than no step at all.
But in my case, having a standing desk, I can get an increased heart rate just by standing still as it's still putting the body to work, i.e. muscles flexing to stay standing, so even with no steps, it's still better than sitting down all day. If I've been standing, say, 3 or 4 hours, then I can start to feel breathless with a higher heart rate. That tells me the body is working harder, just by standing rather than sitting.