That's definitely a feasible explanation (and the one I would assume to be true for AliExpress).

But there is another, slightly less evil, explanation that I know at least some companies have pushed their apps because of: the thinking is that if you're on their website, there is less friction to open a new tab and search for a lower price from their competitors, than if you're in their app. Obviously it's hardly any different - opening a new app (the web browser) vs. opening a new tab in the app you're already in - but the theory is that there's a slight psychological difference.

Of course I'm not saying that trying to prevent your customers from searching for better deals is a nice thing to do. Just adding that data mining isn't the only reason for some companies to want people to use their apps.