The flak suppression was for inbound on a skip-bombing run. Pretty effective against lackluster Japanese flak, as the Japanese disregard for defensive measures left their gunners poorly shielded.
Against emplaced 88s in the ETO, I suspect they wouldn't have fared so well.
I have walked around at Peleliu and looked at the Japanese defenses, granted decades later. It would have been extremely difficult for them to have gotten 88s there to emplace if they had had them. I think it is worth remembering that the physical environment was dramatically different between theaters and that drove the weapon selection.