No, it's not. As a crew member, you cannot be REQUIRED to contact the company on a day off. Number of hours of rest doesn't matter. Feel free to call if it happens to you if you'd like. It happened to me, I didn't call until the next day. They said OK.
Maybe I misread this but there is no requirement to call in when you're on recovery. You can be contacted up till 1500 the day prior to the trip being assigned