Would he really need turn cordination when he is not turning?
The aircraft stays flyable without it, but that is not the question here.
The PF was used to it, we can assume that he never flew without it in a real aircraft. Any aileron input causes increasing drag on one wing hence sideslip, and any bankangle causes change of lift. It is a fine system that you donīt have to even think about those changes because the aircraft systems conmpensate for it on their own.
Without this compensation the lateral SS inputs causes sideslip and any bankangle change causes change of lift. Thatīs why you use some rudder and some nose up input on old aircraft without those systems when turning.
Therefore it should feel different to the normal everyday smooth riding especially with those big inputs made by the PF without autopilot and in roll direct (Alt 2).
We humans tend to feel uneasy with an input, if the desired result is not what we exspect. Look at car drivers on slippery roads, if unexpierienced they slam on the brakes if the car picks up a slight drift and agrevate the situation.