Additionally, I should have considered the possibility that both parties are mis-remembering the interaction. Seems I owe @worldsoup an apology.
@worldsoup I apologize for suggesting you were lying about your experience.
Anyway, if I had to guess as to what really happened, I expect the recruiter told a small, white lie when pressed on why OP didn't get the job.
Probably OP though they'd passed the interview because they got a meeting with the CEO. Or OP thought passing the interview meant they had the job, when in reality there were multiple qualified candidates and Optimizely chose another one.
There's other information in this thread to support this conclusion. I won't rehash it here.
In conclusion: the most charitable explanation is both parties are telling the truth to the best of their memories, and maybe a third party was a bit dishonest in a way meant to spare someone's feelings.