It was always my opinion that they don't need it. Hatch marks were traditionally put in bores to help with brake in, but with a plated bore the rings never really bed into it. As far as I know the rings are made slightly different in design or material to compensate for this. Hatch marks were never intended to be around for the life of the engine, just brake in. Do it to a plated cylinder and I'd think they would be permanent. I know the dirt bike companies tell you not to on their plated cylinders, just rings and piston. Even on the 4 stokes where leakage can be more detrimental to performance. With high RPM 2 strokes, perticularly small displacement ones, as long as the rings aren't being lifted by some aluminum transfer they seal good enough. Hell there's even saws with just one ring like the 288xp, and that thing has no idea its lacking anything.