I wonder if all these rattles on ex demos are in any way related to the rev limiter beatings the cars had in their previous lives?
In all seriousness, pre-registered, fine, ex-showroom car, fine. The first few hundred miles on the car should be run in properly. Full throttle cold starts, rev limiter shenanigans etc aren't something I'd want to happen to my cars engine with 5 miles on the clock.