^^ok but that's different
Notice how Arakibmade it so instead of Diavolp just not being worthy, he just wasn't stabbed at all
Implying that if Diavolo was stabbed, he would have evolved. Hence why Araki had to make it so Diavolo wasn't stabbed at all.
The arrow can deem you worthy but fate can make it so you don't get the arrow at all to prevent the evolution.
Like if Diavolo wasn't evil, he could have gotten KCR.