It’s a skew rebate. To function as a rebate, the blade at the edge has to be a few thousandths wider than the body. Particularly on the cutting side. If the blade is not a little proud of the body, when you plane a rebate, the plane will progressively walk away from the sidewall with every pass. Also, when the blade is a little wider, it gives you some flexibility to deal with the situation where the blade is not sharpened dead flat with the plane sole—you can make small adjustments to make the plane cut properly, even if the latest sharpening has the blade slightly higher on one side.
For example, on my LN large shoulder plane, the blade is exactly 0.004” wider than the body. I wouldn’t mind if it were a coupla three thousandths more than that.
Suggestion: make changes slowly. Test the plane as a rebate plane; hammer tapping the blade into position on the cutting side as you go; Be guided by the results. Also, do whatever Warren suggests .