It's been mixed. My dealer claimed it's normal operation. I've hired an attorney and have endless videos time stamped of the rattle and knock. My noise is definitely changing as I have a start up rattle for 2-3 seconds, then what sounds like change or bolts being shaken in a metal coffee can for the first minute or so (this has progressively gotten worse), and then turns into a knock from the passenger side of the truck.
What you're describing is exactly what my wife's 2018 Expedition is doing. Amazingly, I haven't had any issues with my '17 Raptor, so far (knocks on wood...). Both have right at 23K miles.