I'm not Mormon, but I was married to one. I got that I was safe as long as I never believed. But that once you believe and then renounce, you're at least at risk. Or maybe that was belief as documented by baptism.
Sure, but "feigning belief" is not "belief". I mean, any deity worth believing in would know whether you believed or not. So they'd also know if you really believed, and then renounced. It's like manslaughter vs premeditated murder.