Using a grooved steel on anything with a RC much above mid to low 50s is bad practice, and even then if it has high carbide content (even Chromium) it won't work very well.
Smooth steels can be used on pretty much any steel and even at RC approaching or equal to the that of the steel. It works far better if the intended knife has RC high 40s low 50s. Can be used on fine grained stainless and carbon up into the high 50s. As the hardness of the steel and/or carbide content increases one has to more closely match the steeling angle to the final grind angle (no microbevel) and can still see an improvement.
A bit surprising to me, but I managed to improve some D2 with a smooth steel by using this method. Attempts to use it for a microbevel immediately blew out carbides along the edge. By matching the angle I was able to get a noticeable improvement but this is also very tricky in terms of technique, approaching impracticality.
As mentioned, overuse will lead to brittle edge failure, but if used carefully is still a useful trick in ones bag. Is used industrially to improve surface and increase local load bearing though the mechanism is quite different. On lower RC steels I believe (but haven't done the testing required to say with confidence) that it improves longevity of the edge due to functionally increasing the RC along the cutting edge - again, this factor much more useful on lower RC steel in the upper 40s to lower 50s.
