It's very unlikely that a drone would hit an aircraft wing at combined speed that high - but certainly possible. I'd be more concerned about one going through a windshield at a slower speed and damaging the pilot.
In US airspace, there's a speed limit of 250 knots (around 290mph) below 10,000 feet. Most light aircraft cruise significantly slower (~140 mph for a Cessna 172) and closer to the ground, whether on approach, takeoff, or other, most aircraft are likely to be going slower than that - so this test is at the high end of that range, even if you add the maximum speed of a DJI Phantom (~40mph) and assume it's flying directly at the aircraft.
Your point that speeds are restricted to be lower at lower altitudes is really salient to the discussion because it's an intentional procedural mitigation for collision hazards in the more densely-populated and less-controlled airspace down low. Drones were but a glimmer in anyone's eye at the time the regulation was emplaced, but the same theories are still relevant.
Bear in mind though that the under-10,000 ft limit is knots of "indicated airspeed", which is a constant-dynamic-pressure pseudospeed uncorrected for density. 250 KIAS at 10,000 ft is about 290 knots/330 mph relative to the airmass, and sometimes up to 10 kt faster on a hot day.
In US airspace, there's a speed limit of 250 knots (around 290mph) below 10,000 feet. Most light aircraft cruise significantly slower (~140 mph for a Cessna 172) and closer to the ground, whether on approach, takeoff, or other, most aircraft are likely to be going slower than that - so this test is at the high end of that range, even if you add the maximum speed of a DJI Phantom (~40mph) and assume it's flying directly at the aircraft.