Genghis surely the ASI is less accurate (admittedly not by a huge margin) during a steep side slip due to the airflow not going directly down the pitot tube? For a side slip to be effective, by definition, there will be a large amount of yaw taking place.
I tend to be nose down and feeling the aeroplane's reactions rather than looking at the ASI at this point anyway. The ASI is virtually ignored until I'm approaching the hedge. Maybe this is because I invariably come in high and sideslip to the threshold.
javelin most aeroplanes that you would take into strips that require sideslipping as a skill will perform the action without a problem. The exception being certain models of the C172 which will tuck their noses down when sideslipped with full (40deg) of flap applied. Allegedly. Possibly. Maybe.