Once you acquire enough of a feeling for a foreign language that not every bit of your skill in it comes from somebody telling you that a particular thing is said in a particular way, you are doomed to live with a constant suspicion that your feeling is somehow off in a way you don’t recognize. Usually it can be suppressed and ignored, but sometimes it can’t, and occasionally it has to become a question. (I expect this is a fairly common experience.) This was one of those.