This is a second hand quote that in its original on CNN is the transcript of an on air interview.

Reading both I think its just awkwardly stated. He isnt saying that Truman was not a supporter of NATO forming on his watch, it was very much something he ended up supporting, and the US was a driving force behind. Indeed he had to fend off some opposition to ratification in the Senate and even then the final vote was 82-13 with calls that the US was abandoning its traditional position of friendship with certain allies but fundamental avoidance of entangling commitments.

He is just saying that every President from Truman on down held the same fundamental position on NATO's structural value proposition.

For more on NATO and Truman you might want to take a look at this stuff from his Presidential Library: https://www.trumanlibrary.org/nato/nato.htm