The aldi chisels are likely made of inexpensive drill rod of some sort (there's a whole line of chrome vanadium steels from 0.5% carbon to at least 1.2% or so). If I had to guess, I"d guess that aldi's chisels are some of that drill rod with about 0.8% carbon or maybe a little bit less, with a little bit of chromium and vanadium (and maybe molybdenum). Vanadium increases potential hardness, , and the other two in small amounts generally make the transition target for hardening slower (meaning if you miss a little in a splash type quench on an assembly line, it shouldn't affect much).

I have the same pattern of chisel (HF used to sell it). I know my chisels aren't more than about 58 hardness. Someone here in the states tested a bunch of chisel and their aldi set struck about 61.5 or so. The difference between those two for edge holding in monstrous. 58 makes chisels that are really only fit for softwood until you introduce the unicorn trick. 62 hardness makes a really nice chisel for just about anything.

re: the process - on chisels, I try to use the corner of the wheel on the back so as not to remove anything from the back. I don't want a double bevel, but on a plane iron, a little of that is no big deal. I don't want to overcomplicate things, but if you wanted to target a chisel that doesn't dive in the cut, you could go a little lighter on the bevel side and just a tiny amount of rounding on the back, but a chisel that feeds straight does so only at one cut thickness, so it's not worth it to me.

When I did the test in the article in wood central, it looks like I got into just a little bit of buffing compound on the back of the iles chisel, but the others show no abrasion on the backs (which is what I'm hoping for). The trip across the back on the corner of the wheel probably isn't necessary. Belt and suspenders.