She might have noticed that Han is rarely ever the first person to start walking somewhere. Often, it's because he doesn't like having his back to people - he does hang around in shitty crowd back home, after all. There's an obvious benefit, however, to letting Nat take the lead when they're going somewhere.

He's not sure that he would ever tire of this vantage point.

It would be a lie to suggest that Han, when they were theoretically 'looking at the bike', wasn't eyeing the woman on it as much as the machine. Oh, he glanced at the bike, sure. It resembles a speeder enough that he thinks he might even be able to figure out how to ride one. If someone was to leave a vehicle like that in his care for a couple of hours.

He finds his eyes increasingly drawn to Natasha, though. And he knows she's at least indulging his attention on some level when she takes that forward lean. "Oh yeah. I like what I see." He murmurs, with a subtle nod of appreciation. "The bike's alright too."