Huh. This is their newest discord announcement, just two hours after that IGN article has been updated
Thanks for letting us know that some PS Plus subscribers have been unable to access the free next gen update of Fallout 4 on PlayStation. This issue has now been successfully resolved. Subscribers who have previously received Fallout 4 from the PlayStation Plus Collection should now be able to access the update as intended.
I still see it with a price. Some users have reported that it’s fixed??
Edit: there’s a new menu to add the PS5 version to your library, currently only visible on the console. The PS app and web store don’t have it