Could Bernard’s vision or memory have been altered to remember choking Elsie, when in fact it was someone else?
Westworld being Westworld, there are any number of ways to interpret that remark.
Only two episodes remains this season, leaving it unclear if Westworld will provide any additional answers on Elsie’s disappearance, but there’s always Season 2!
So I will only say this: I will answer your question with this question.