Topsoil is made up of both organic materials (humus) and inorganic materials (clay and silt). I have used soil I dug up from a silt deposit on a river bank, which was high in very fine sand, had some clay, and quite a bit of humus. I also used some soil I dug up in an area with lots of brush and trees. And, I have used soil I dug from the planted areas around my duplex. All of them worked ok. The river bank silt was the most stinky until I had it mineralized, and I think it grew plants the best, but not a lot better than the other soils.
The packaged "topsoil" I bought at the cheapest price I could find, at a hardware store, was mostly shredded bark and bigger pieces of bark, plus sticks and stones. I didn't like it at all, and my soil layer never did stop generating "air" bubbles, which were obviously laced with hydrogen sulfide. So, my personal preference is real topsoil, not packaged "topsoil".