The 'need to nudge' should really described as 'might need to nudge' as 'the nudge' is not a requirement but is a way to satisfy the real requirement.
The real requirement is that at the point of making the auto lane change (not sure if its when indicating too, but definitely sure its needed at the point that the maneuverer starts), you need to have satisfied sufficiently the 'drive must be paying attention check', which is basically satisfying the hands on wheel with sufficient torque.
If the car does not detect that that requirement has been satisfied, then it goes into prompt mode, by which time, a 'nudge' (or other equally sufficient methods to satisfy the torque detection) will be necessary to be performed before the manoeuvre times out.
If you don't normally hold the wheel in a way to continuously satisfy the torque requirements, then its easy to think that its 'the nudge' that is needed.
All these observations are from before the in cabin camera was activated. Torque requirements may now also be influenced by visual driver alertness que's and are likely to vary between geographic regions especially if those under UN/ECE regulations start to benefit from the formal introduction of L3 rules - last I read, those will not require any specific checks, just to satisfy a check every (iirc) 30 seconds that may be in the form of a physical interaction (ie steering torque) or visual driver alertness - although auto lane change may differ.