For a long time we've been told not to snack after supper. By long time I mean most if not all of my life. For those of us that don't snack or eat after supper we probably have autophagy going on during sleep. Regardless of what specific diet we follow.
Prior to a few years ago, that was normal stuff. But for some reason lately people want to call it fasting. I guess if that 12 to 18 hours is something you want to call fasting then go for it if the word gives you incentive to not eat before bedtime.