It sounds like it might be detail-specific to that outlet. Did they make it clear when you submitted and / or when they accepted the piece that a publication date would be set later? If the second place does accept it and gives you a firm date, and you're comfortable with them - I'd withdraw it from the first. Waiting to hear back on a sub is one thing (and normal), but ghosting after a clear decision is not on the up and up, at least not without better communication on what to expect.