Thanks for the responses, @Thedrellum and @novicewriter. The magazine that was bothering me the most states in the submission guidelines that it aims for a two-week response time and instructs to query after a month. From what I surmise from
its listing in The Grinder, that market is non-communicative. I've queried and waited more than two months, total. I'm no waiting a half-year for a response for a market that competes with fifty others.
Maybe more writers will see the Dead Letters percentage go up and update their submissions for more accurate data.
After more consideration, I've decided whether or not an official withdrawal is worthwhile depends on the submission and publication process. I won't bother for email submissions that didn't receive confirmations.