I love how this whole chapter was D'arby freaking out. This was definitely one of Jotaro's most badass moments.
Imagine if Jotaro never looked at his cards at the end, and it was just left as a mystery what cards Jotaro had?
If D'arby had called then he would've obtained Jotaro's, Kakyoin's, Avdol's and Holly's souls on top of Polnareff and Joseph. He would've undone all their efforts with one word.