Here is a head-scratcher of a situation. Suppose an author has a novel currently under consideration at a publisher. It has been some time since initial submission, but it is still within reasonable timeframe of review. Suddenly, a different publisher provides feedback making it apparent that this novel might be a good fit if submitted, as it is similar in writing style to another novel submitted to that publisher, but addresses the criticism provided therein.
Remember, nothing is guaranteed, and the publisher made no promises of any kind. This (somewhat) hypothetical author is acting purely from his own perception of the situation.
If an author makes it a point to avoid simultaneous submissions, would it make sense to either withdraw the novel from consideration elsewhere, or to send a follow-up query to the publisher currently evaluating it?