I don’t think it's specific to this version but, I used AP all the way along the A47 to my destination only disengaging at roundabouts.
my journey started on dual carriageway and it engaged at 70mph dropping to 60, then 40, then back up to 60, down to 30 and so on recognising every change faultlessly.
the return journey was engaged at 60mph and changed up and down all the way home until we got to sections of dual carriageway where it would not rise beyond 60. This leads me to believe that the first speed limit that AP engages at, is the max it will go unless re-engaged at a higher speed.
this might explain why some owners don't get the auto changes they expect. I suspect that if engaged at say 40, it will drop to 30, increase to 40, but ignore a 50, 60 or 70.