It's also possible he lied about his end date to throw suspicion off. Or he may be still working for the company and used someone else's resignation to pin the blame on them.
That’s what I would have done. Planting a few lies to protect your anonymity can’t hurt. Maybe they quit months ago, or maybe they didn’t even put their notice yet.
Maybe “he” is a “she” - quite right what you say, there’s no reason to believe their details.
I would say what they describe about their employer is probably true. I’ve had similar experience of companies making every last buck off their “human assets” but thats how profit works: you take money off others in exchange for promised benefits.