Just for y'all's information, I don't know the answer to that. It would be interesting to look into why only system(1,...) wraps things in cmd /c "..." in a way that triggers this bug. To figure that out, I'd read the code that I linked to above. I did scan some parts of it earlier but not looking for that quirk (I initially missed your point that the "1," was required).
But why not just include a trailing space and then none of that will likely matter? (And include a comment noting that the trailing space is required to work around a bug in: cmd /c "cmd /c ...".)