The part about cookies and pizza turning out fine really hits home, because that was my exact excuse for years. I always thought my oven was close enough, and for most things it probably was. Then I started baking bread and learned that dough is way less forgiving than a cookie, which does not care much if things run a bit hot or cold. So I do not think you were dumb at all, and your sister's "bake by feel" line only works if you already know what the right feel is. These days there is a cheap thermometer hanging in my oven and it stays there.

Did you see that thread on the flooring forum where a guy tested both ways on the same staircase? He glued one flight and tacked the other, then came back a year later. The glue down held fine but the tack strip one had a few spots pulling loose right at the nose. I've also heard that a lot of it comes down to your subfloor and whether the stairs are wood or concrete. Twelve jobs is a lot to second guess over one guy's opinion in Fresno.