It;'s both really, but the in-air deployment case can get very bad, very quickly.
GS destroy a LOT of the lift on the wing. To the extent there may be almost NO lift.
The gear is designed to a 10ft/sec impact. Drop an aircraft (or anything else) purely free-falling from 10ft and the impact velocity will be of the order of 20ft/sec. Twice the design velocity, 4 times the design energy. That's going to break a lot of bit of aircraft if it happens.
(You'll note that the radalt threshold for "on ground" is usually set down at 5-6ft, to minimise the impact in the event of a deployment at the radalt limit)