That's fair and it works in Sterling's favor, which I believe is your argument, since he relies more on movement and positioning to score goals than natural finishing. However, if we are adding context to xG, then maybe we should also talk about the fact that it is a shot-based metric and so it doesn't show up if the player didn't even shoot.It's a good way to assess a tool but it's incomplete.
Some players might not overachieve, but they could have significantly higher xG than average, due to brilliant movement and dribbling for example. The overall goals in a player who overachieves their xG and a player who doesn't but has really high xG to begin with could turn out to be the same.
This isn't an argument against Kane (or in favour of Sterling) btw, it's just me saying xG can be interpreted in multiple ways, each with their own value. The level of analysis can go a lot deeper if you choose it to.
And just off the top of my head, I can remember many instances where Sterling was 1v1 against the keeper, but didn't shoot (and the keeper collected the ball), or he was in the box trying to shoot but couldn't connect, or he kept cutting inside only to lay the ball off at the final moment instead of shooting.
So in terms of accounting for golden chances that would probably have been converted into goals with a high degree of probability had someone just taken a shot, I would say Sterling would rank lower compared to the names that are being discussed.