I assume a combination of muscle memory, timing and multiple takes.
When I played baseball and softball the pitch was often too fast to acquire the target and swing the bat accurately for a hit. The trick is to anticipate and using the body language of the pitcher time the swing and at the last minute make minute adjustments after it was possible to see the ball and determine it’s trajectory. That is the whole purpose of the changeup in pitching to offset the rhythm and disrupt the batter’s muscle memory enough to force them to depend on their vision which just isn’t adequate especially in fast pitch softball because of the much shorter distance to the pitchers mound. I suspect too that 70 feet for a airsoft pellet is the optimum distance where it has slowed sufficiently to see it but not yet so much that it drops to the ground. But even given all of that it was still a pretty good feat.