The US govt issued a quality control board report on this issue and several others in about 1963. The flash suppressor caused many accuracy errors, both for point of impact and group size. Causes included off-center barrel threads which misaligned the small front end hole to the axis of the bore, standing droplets of water on the bottom web deflecting bullets, and improper machining of some of the small internal faces on the muzzle joint. By removing the flash suppressor the groups moved somewhere else, and were smaller.
Most Norincos have an open bottom web and a larger front end hole. If it caused problems with accuracy, it would have been addresses openly before.