I have always thought of it as how graffiti taggers work. They are always tagging over each other’s work. The last one to paint gets the most exposure but you can still see remnants of more recent taggers the lay under the topmost. Eventually the oldest stuff just gets covered completely. They don’t necessarily pick their canvas because there is other work they try to cover up, they pick their canvas for the location and exposure.
If answering the email requires writing a book to anticipate all the possible questions or options or complications that might come up, then no it’s not disrespectful to call someone instead.