You are oversimplifying the level of chemical interaction and making incorrect logical conclusions.
The school logic of math doesn't work in chemistry: “In both the first and second cases, sulfur dioxide is used, so the reactions must proceed in the same way".
In inorganic chemistry, everything is much more complicated.
The reaction diagram shows only the approximate reaction products. This is NOT an accurate quantitative diagram of the complete interaction of chemical elements, unfortunately. This often confuses newbies.
It would take quite a long time to list the points on which reactions differ. Therefore, strictly speaking, you will not be able to provide equivalent equality of reaction conditions for SMB and pure SO2. Therefore, the reaction results will always be different.