Did Truman Not Understand Likely Civilian Toll of A-Bombs?

Terrific new article by the invaluable Alex Wellerstein raising a question I haven't confronted in years:  Did Secretary of War Henry L. Stimson's well-known success in getting the great cultural city of Kyoto taken off the atomic hit list mislead Truman into thinking the other targets were primarily military and not large teeming cities?  I'm not convinced.  I think Truman was insensitive to that to begin with (as were so many American leaders, military and even some scientists) but the point is worth considering.  If true, it does show how early clueless leaders can order slaughter, especially if shielded by subordinates.  Truman did describe Hiroshima merely as a "military base" in his historic announcement and I've always figured that was pure propaganda, but who knows, maybe he thought that was (mainly) true.  Nagasaki happened because he didn't care enough to halt for a few days--it was assembly-line massacre.