The biggest issue they had was trying to force that after the fact.
Had they come out and made it very clear from the beginning this is the requirement and enforced that from the get go, that’s a different situation. But in the case where people bought the game and Sony wants to change the terms of the sale, you don’t do that.
If they’d have required a PSN account at launch, then they’d also have had the flexibility to open it up to signing in from steam etc etc, then they would have come out looking more pro consumer and looked better as a company. Whereas now it’s great they did a U Turn, but now you likely have people out there who are fed up already and may be less likely to purchase other games from them in the future.
Except Sony DID state clearly that a PSN account would be required on its store page from the start. I don't mean to defend them, but it CLEARLY STATES IT as Required. Not Optional. Required. And Sony did intend to enforce it, the Devs themselves have mentioned it.
Requires 3rd-Party Account: PlayStation Network
More importantly, it was only deferred at the request of the Devs, because they wanted to get as many sales out as possible, and quickly get as many people into the game as possible by avoiding some server issues. It's obvious many didn't read the fine print, and admittedly, it was underhanded for the Devs to insist on delaying mandatory PSN account linking partly for financial purposes. But it was always listed from the start, and it was also repeatedly mentioned that Sony would eventually enforce the requirement. The terms never changed, only the lack of initial enforcement.
In fact, despite all the drama, and the supposed refunds, player counts remained almost entirely unchanged according to SteamDB. If anything, the ones likely refunding were probably the ones who quit playing already and were taking advantage of the drama to get their money back, as well as in the regions where Sony already began to pull the game from anyway due to a lack of PSN services there.
This backtracking ultimately just makes Sony look good, "caving" to the playerbase. But the stats show that despite supposed boycotts and refunds, the majority of the players playing didn't care enough to actually drop the game enough to affect actual statistics. Odds are more likely they'll mandate PSNs for new sign-ups in serviced regions (already easy enough to cross-check with Steam given Steam's pricing and game availability changes by region), and make it optional for those outside serviced regions (where the game hasn't been pulled from the storefront yet, at any rate).