IF it is in really good condition,grab it. Excellent price and very good lens. Yes, aperture is 2.8. What Tony might have been trying to convey(or was just plain uninformed...remember, his job is media personality, not photographer, he gets millions every year due to having over a million subscribers and not because he is an expert in anything in photography. I stopped viewing his channel after just too many bad statements intended to push particular brands he gets kickbacks from. there are very few working pros on youtube.) was total light falling on the sensor, which would me more on Fx but the image image circle is the same, Fx/DX but the DX sensor only gathers the light from a DX image circle. In any case, a F stop 2.8 with a T-stop of 2.8 will be a lot brighter in the VF and on the sensor so the ISO can be lower than any of the slower variable largest aperture DX lenses. That lens, for field sports would work BETTER on DX because of the narrower field of view equal to a 300mm lens on a Fx body. That is why the D500 DX is such a popular sports and wildlife camera compared to D850.
Get it. If you don't someone will grab it. That model, A009 has a very good image stabilizer system that allows shooting hand held to pretty low shutter speeds. But you will still need high shutter speed for action sports. If the shot is not at full action speed, such as at the end of a play or detail of a huddle, lower the shutter speed for clean noise free crystal clean images at 1/160-1/200. It is best to use the center focus point, it is more sensitive in that camera and is the sharpest part of the image circle projected onto the sensor. In any low light situation, use the center focus point. Since the max aperture is wider than what you are probably using, it will allow the AF system to work better because it has more light to worth with. In every possible way, a 70-200 2.8 wide open the camera itself will work better than a kit 5.6 zoom, regardless of light. The lens is about 3 pounds so consider a sling strap so it caries the weight effortlessly when not up to your eye. 3 lbs is not heavy but after long event, your hand holding will be lot steadier throughout if not supporting all game with one hand.
Oh, yes, grab it....