Usually when we put something in a caution section that is technically still correct, it is reflecting something that can be seen in the wild, but that we don’t want people to accidentally memorize over the main point, as that is generally the one that will appear on exams, which our reviews are geared towards.
However, we should have a warning for this that would be something along the lines of ‘Can you try an unabbreviated version?’.
In connection, we have recently written a whole stack of default hints as above and are planning on revamping all of our grammar points soon with far more leading/directive hints.
In regard to the omission of か itself, although the nuance is the same, grammatically it changes the previous phrase into a simple quotation rather than a question, so in that way they are quite different.