Grooved steels, of decent quality, are said to be about 20% harder than typical kitchen stainless cutlery. In comparison to a kitchen knife of typical low-alloy stainless at 55 HRC, that means the honing steel would be around 66 HRC. That's more than hard enough to remove metal (i.e., sharpen the edge) on a kitchen knife; especially with the grooved/ridged surface, which makes it cut exactly like a hardened steel file. If you want to see if it's removing metal, just wipe down the honing steel with a clean paper towel moistened with Windex before and after you 'steel' the blade, and look at the dark swarf picked up on the paper towel after you've used it on the blade. In fact, sometimes you can see, under bright light, the reflective shards of metal left on the steel's ridges after honing on them. Other evidence of their ability to remove metal is seen in kitchen knives (especially chef's knives) long-maintained on steels alone. They develop a recurve in the central portion of the blade, due to heavy steeling for such a long time.
Steels do 'align' edges on knives, and that's what they're mainly intended to do in practical use. But it's not necessarily the only thing they do. If one wants to 'steel' a knife by only realigning the edge, a polished (smooth) kitchen steel works well for that, without removing any significant amount of metal.
David