if the "pen" is replaced by half a matchstick, representing a very light aircraft rather than a heavy jet, when the "gust" is applied the very lightweight aircraft will react quicker (catch up quicker) it's airspeed will change relative to the air parcel, but by a smaller amount and for a shorter time than the heavy aircraft as the inertia, body at rest etc, takes over.
Indeed, the teaching/thought on windshear for years has been that airliners are much more prone to potentially fatal problems with windshear than light types, especially in the rapidly reducing headwind situation, due to the generally much higher "m" in the "mv" ....interesting to see some here talking about it having significant effect on light aircraft.