It's not typically fake. They'll strap a camera on an athlete (current or former) and let 'em rip a run on the course. If a current athlete the camera is typically a chest-mounted GoPro or similar, so it gives a strange look. Former athletes have more flexibility with camera mounts. Some do helmet mounts, others use a monopod stick that GoPro's software can digitally erase, giving a bit of a "drone footage" look. Ligety used a helmet mounted monopod stick to get some funky shots over the years.
And then there are follow cameras, which are typically a retired athlete or a coach skiing behind an athlete in a "flying wedge" to get the footage. This was the case with the Cortina slaloms, where the forerunner being filmed didn't wear an on-body camera.
And before I pass it over, Hans Knauss used to ski all of the World Cup DH tracks with a handheld video camera and a small backpack containing the remote broadcasting hardware. He'd occasionally flip the camera around to film between his legs, looking behind. His narration of these runs is worth the price of admission.
If you want full on "looks like Bode Miller Ski Racing PS2 game from 2003" appearance, look at the Doug Lewis camera footage from Salt Lake 2002. That contraption was quite stable but would've been quite a problem had he crashed.