What is 'wrong' with an attempt to describe ground effect as a result of mass being partially supported by a 'compressed' cushion?
exactly...this 'unseen cushion' in flight, becomes apparent next to the unmovable surface, and is how ground effect vehicles maintain altitude.
Ground effect is relevant, by illustrating the issues associated with using Bernoulli's principles to explain that the airflow over the top vs the bottom of the wing creates lift.