PBA: I know of several Sefardi Poskim who allow their followers to be Mattir Neder on fish and milk. In fact, many Sefardim are Noheg L’hakel anyway.
PAA: R’ Ovadia is famous for holding (by several different logical paths) that Ashkenazim should be Sefardim. Ashkenazi Poskim rejected that Psak of his. This is just an example of that. (And see the harsh words R’ Ovadia has the for TZ”E when the TZ”E tried to Pasken for Sefardim against R’ Ovadia.)