I would be surprised if the current version of AP is reacting to indicators. I've noticed similar behaviour whilst on NoAP, when in the overtaking lane the car will slow to match the speed of the car/lorry on the inside lane, even when the car in front is pulling away. I have never quite found a reason for it doing this myself or on any of the forums.
However, I have just been out to do a full test on 28.2 for my youtube channel and whilst I did see the same behaviour a couple of time, this time the car waited for a bit and then speeded back up to max setting without me needing to press the accelerator pedal. I think this is new for 28.2?