A higher level of hop oil (or pretty much any vegetable oil, really) will indeed reduce foaming. But that is primarily of academic concern, because you simply *can't* play with the hop levels without affecting the flavor. A brewer will perfect the taste, aroma, color, texture, etc. of a beer before they even start thinking about practical concerns such as blow-off. Which is fine, because as I said, there are already solutions (pun intended) for blow-off, which don't involve reformulating your recipe.
A brewer who saw excess foaming in his dubbel, and added hop oil to try to combat it, would find that he was no longer making a dubbel.