“Highest rank” in this picture is referring to “highest rank obtained by that person” and not the highest possible.
It uses the same wording for Vance, who was a corporal.
Edit: unless someone was an officer and served in Congress, which has probably happened and I don’t care enough to look it up
Read statement four again. It clearly states he is the highest officer to have served in Congress. This is inaccurate. I have personally met a 2-star General who is a Congressman from Mississippi.