It will shoot just fine being ground flush. Just makes it a bit trickier on the interpreter to know where the boarders of the weld are, but that's what measuring tools are for. There are plenty of radiographed welds out there in the world the require a flush contour for the next assembly. Depending on the fabrication standard you are working to, if you have any suck back in the root to where the weld thickness is now thinner than the base material thickness, you may fail your RT inspection.