Helldivers2 was supposed to used Sony account linking at launch but due to all of the login issues faced, it was agreed it would be temporarily disabled to try to alleviate some of the issues. Which I remember that being announced at the time by Arrowhead.
Sony then mandated that it be reenabled.
Fully agreed on the issues faced by people where Sonny is not offered/supported which is why it’s so important that people include that in any negative reviews they leave so that Arrowhead can use those reviews in discussions with Sony.
Make no mistake, this was not a new policy and my understanding is that any Sony studios game has this requirement.