(SEE FOLLOW UP) Halo Campaign Evolved's PS5 port has strict split-screen co-op requirements: both players need PSN memberships and Xbox accounts

Follow up response on X (formerly Twitter):

We incorrectly stated that PlayStation Plus is required for local co-op splitscreen play. Local splitscreen co-op requires a PlayStation account for each player but does not require a PlayStation Plus account.

Original quote from the article:

On PS5 specifically, both split-screen players will need to have an active PlayStation Plus membership and a linked Microsoft account. Steam players will only need to link to a Microsoft account, while Xbox Series X|S players will only need an active Game Pass subscription if they want to play online, as expected.