I can get that

he is only in the movie a few minutes , and doesn't have a whole lot of lines

so by the time this movie had come out , Eisenhower had already been President for 8 years , pretty much the entire world knew what he sounded like

if the actor didn't sound anything like him , it would have been pretty noticeable

the one actor I never bought into playing Eisenhower was Tom Selleck , a decent enough movie , but not for a second , I ever felt like I was watching Eisenhower

---