I doubt anyone of is truly scared of anyone. It's a money and power game. Bud doesn't realize he isn't worth his asking price (60-40,) and Arum isn't going to negotiate with any PBC fighters.
As far as Bud losing to Porter. I can't see it. Porter doesn't have the skillset. Porter's at his best when he can maul and bully guys, but Bud is just as strong, and has the stiffer/harder punches. I'd say Bud is as strong as anyone at 147. Brook laid the blueprint on how to beat Porter years ago and Thurman followed it up. Move, box, and tie him up.
I hate triangle theories in boxing, but Brook figured out, and neutralized Porter easily in their match. Yet Brook showed he had zero answers once Bud switched to southpaw. It'll probably be an ugly (Porter) type of fight, but I see Porter losing the UD a la the Thurman fight.