I had assumed that the browser part of explorer simply hosted another control or collection of controls. Though explorer is more than a browser. It also acts like a desktop shell. Though I understand this is probably the lower priority on the wine developers list. As integrating into Linux desktop is probably the preferred and most used mode. I thought that sharing reactos explorer and working on making a complete explorer(including extensions) would be the goal. Though now I'm saying it I feel rather silly, as this really is the least important part of wine.