Meaning of "scan" in "that doesn't scan in English"

In an answer to another question this sentence was proposed:

Was it specifically mentioned as part of their teaching, or they just happened not to have killed anyone?

In comment, another user wrote:

That doesn’t scan in English. Sorry.

What does scan mean in this context? I've searched the online dictionaries I normally consult (NOAD, M-W, Dictionary.com, TheFreeDictionary.com, Oxford Dictionaries Online, Cambridge Dictionaries Online), but cannot find a meaning other than "(of verse) conform to metrical principles" (NOAD).

It's a figurative extension of scansion. It just means that the words don't flow naturally in English.

Technically, "scan" is usually used as your dictionary suggests to mean "conform to metrical expectations/tradition".

But I don't think the person in question is using the word with any technical sense. What they really mean is "In some vague, unspecified way, I don't like the way this sentence sounds".

[If pressed, probably what is raising their objection is that the sentence sounds imbalanced as it has the inverted structure "Was it..." in the first part, but no inversion in the second. The reader half expects you to write "...or did they just happen..." to keep the balance.]