Personally, from my experiences, I really do believe it's who you talk to and how the situation is handled. Sometimes it needs to go beyond the normal Apple representative on the phone to reach a positive result.
Sure, I'm willing to believe I lack the necessary powers of persuasion/charisma to get a free replacement in this case. FWIW, I think my interaction with the Apple Store employee was polite/honest/reasonable, but who knows, maybe I'm a horrible judge of that too.
In any case, my main purpose is really to let people in the same situation (i.e. out-of-warranty swollen battery) know that a free replacement is truly YMMV, not "always". It might be easier with the iPhone 5 since there's a publicly advertised Quality Program that covers it, but not for other models.