Yes, when you fall your arms tend to shoot out faster than your body falling. Otherwise you would fall on your face.
What if you’re in a bulky space suit?
Also, the dude in the video doesn’t NOT claim that slow motion technology didn’t exist at the time, but there would have been no way to create a continuous slow motion shot for as long as necessary to fake the footage from the moon. That’s the point. And as I said above, in that other thread I posted a video of three VFX artists reviewing other footage from Apollo and concluding those shots wouldn’t have been possible before modern CGI. Compare and contrast the Apollo footage with the 2001 film.
As has pointed out above, you can see from the way the dust moves as they walk that they are in a vacuum.
TL;DR - the people who say it was fake are not knowledgeable about cameras, film or special effects.