When the inclusion projection of a collection field is not at the first position in the pipeline, the field inclusion logic for nested paths can lose the path arrayness of collection fields.

This will not lead to an incorrect rewrite, but it is an omission and can be improved.

// Assume path arrayness reports a.b.c is non-array.
[{$match: {m: 1}}, {$project: {'a.b.c': '$x'}}] 

We lose arrayness for 'a.b' and 'a.b.c', just 'a' remains as known non-array.

canPathBeArray(nullptr, "a.b") -> true when it should be false