You are looking for edge material being removed/polished. If the removal doesn't get as far as the base/side edge junction (the part of the edge that should be sharp), then you aren't doing any sharpening, just removing excess material. If you are removing material from the base/side edge junction then you are sharpening the ski's edge.
When I was in my early 20s, I shared a house with some other poor college students. One of my housemates thought that washing the dishes comprised putting dirty dishes in soapy water, sponging them off, rinsing them, then drying them. That, in fact, was the sequence of operations that the rest of us used too. The difference was that we were monitoring as we went whether the dishes were actually getting clean. If not, we would re-do one or more of the steps - possibly with variations, such as using a scrubby - until they were clean. She would go through the motions, but many of the dishes were still dirty at the end of the process.
Similarly, by far the most common failing that I see in the other amateur tuners among my group of ski friends is that they do a lot of tool sliding, but their edges are not actually getting sharper. The missing skill is the ability to know whether an edge is meaningfully sharp or not, and to tweak the process - e.g., sidewall removal - accordingly.