This show started as another anthology series and it was certain from the start that the show was gonna have 13/15 episodes, Ryan is not stupid he did not expect or probably want a 22 episode series order for an anthology series.
After the failure of the whole Tuesday line up (The Grinder's ratings were even worse but that got a full series order) thinking FOX didn't order a "full season" is just so stupid. Sorry but stop with this nonsense
Also I thought the finale was somewhat good, one of the killers got away with murders, and didn't receive a punishment which is a rare thing for a horror movie/series. It would've been better if Ryan did what he promised and only let 4-5 people survive from the main cast and not end the show with a cliffhanger. You don't end an anthology/mini/limited series with a cliffhanger, that's just cruel.