That's just not true at all. Let's say there are two theories for a truth, A and B. I don't necessarily have to commit to believing theory A or theory B, but I can lean more towards believing and being more convinced by either of them. If I happen to believe theory A more, who's not to say that developments in theory B could cause me to shift towards theory B later down the road?

But what happens to the close-minded is that they're either more sold on theory A or B, and henceforth stick to it and cease to keep up with the other theory. Because they've already written it off as "wrong" or "bad" in this case.

Thinking that you have to commit to beliefs is just intellectual laziness. It's more comfortable to assume that you have all the right and correct takes and therefore there is no need to challenge yourself anymore.