I imagine being reminded that he is the acting president is part of his daily briefing from his handlers; but that doesn't mean that the doorknob remembers it all day long.
But yes; he has a 'pen and phone' and so why doesn't he attempt to Executive Order a return of Roe v. Wade into existence? Probably because he doesn't really MEAN it. He's just playing his all emotions -- but ZERO thought processes -- political base. But fortunately for Dementia Joe; he doesn't have to put any effort into playing THEM.