Flaps 35 is a normal landing flap setting for the DC-10/MD-10 as is Flaps 50.
Looking at the video they were at Flaps 22 and when they selected Flaps 35 the gear unsafe warning went off (which cannot be silenced) and prompted them to lower the gear.
If the crew was fast, the gear would have already been out. It has a much higher extension speed. (Around 260 IIRC) And any pilot would be using the gear well in advance of getting that low.
Anybody can fly a round airplane....