I think the relationship is real. I suppose since Harry and Olivia were dating they decided the publicity would be good to generate interest for Don't Worry Darling hence the wedding papwalk. We would've gotten more pap walks for publicity but Jason questioned their timeline and that ceased. I hope the cast and crew weren't affected by the media storm that ensued with the cheating rumours.

You could argue that this amount of publicity wasn't needed as the movie also has Florence Pugh, Chris Pine and a great cast but there have been films with A list casts that didn't actually do well at the box office. I just hope their relationship doesn't overshadow what could be a great movie.