Logging in again to comment on this.
The Reddit user in question is getting laughed out the door because they are in the US, where PSN accounts are easy to sign up for, and is planning on suing on behalf of aggrieved customers in other countries, which you are unable to do under the US legal system. The user has no legal basis for the case, as they don't live in an affected country and clearly has no idea how the US legal system works, will be laughed out the room again by any lawyer worth their salt, and as such the suit will always remain text in a post on r/Helldivers. And if it does happen, I wish the user luck with getting back their money on a case they have no chance of winning.
As for the idea that this is a retroactive decision or a bait-and-switch, may I point to the bottom of this Steam announcement a month before release? Sony always had this planned, it was just disabled because the game blew the fuck up at launch and broke the account linker making people unable to play.
This is a failure on Sony to restrict sales in countries where PSN is unavailable and for improperly communicating to players that this requirement will eventually come back, and if launch went according to plan and they got 50k - 250k players at launch as anticipated and not close to a million the requirement would have never been waived.