Question about Harry Truman

Not from what I've read, this was my question too, though I was suspicious. So far nothing says that it's right. Too bad since it's an interesting suggestion!

Yes. The Truman library website clarifies this. His middle "initial" was a name he gave himself due to tradition during one of the wars. It was in honor of his Grandfathers whose middle names both started with "s."

I have also heard his middle name was Simpson. However, the library and several other sources make no mention of this. So, the library website is reliable enough to conclude no middle name.