Sure, you can infer all you want, but I'm talking about whether there is grounds for legal proceedings. There is a higher probability that a defense lawyer would take a case where the rejection letter says "you weren't a good culture fit" vs "you didn't get the job". Companies simply do not want to even open themselves up to litigated, even if they've done nothing wrong. Further, there is no commercial incentive to tell the candidate anything other than "you didn't get the job", so why bother?
> People attempting to give honest explanations will sometimes explain things poorly in a way which indicates a prohibited
That's precisely my point. It's very difficult to explain to someone that they've been rejected for a position even in the most sincere and nicest way possible.