Yes.

Constant Aperture is a reference to a zoom lens' maximum aperture at all focal lengths.

It does not mean that it is the lens' only available aperture setting. That would be a fixed aperture lens.

It some ways it is easier to shoot in aperture priority exposure mode with a constant aperture zoom lens than with a variable aperture zoom lens.

(The following is applicable when using any Nikon digital camera with a Nikkor/Nikon lens, or third party lens in the Nikon F-mount, that does not have an aperture ring, such as the lens in question, the Nikkor AF-S 24-70mm f/2.8G. It is also the case if you are using an older Nikon or third party lens that does have an aperture ring but the camera body you are using requires the ring on the lens to be locked at the narrowest aperture setting.)

Let's say you are in a low light situation and you want to use the widest aperture at each focal length of a variable aperture 70-300mm f/4-5.6 lens. If you start out shooting at 300mm the widest you can set the aperture is f/5.6. When you zoom out to 70mm, the camera will preserve the f/5.6 aperture you selected at 300mm. You'll need to reset the aperture to f/4 while the zoom is set to 70mm. Then, when you zoom back in to 300mm the aperture will be forced back to f/5.6.

On the other hand, a constant aperture zoom lens allows the same maximum aperture at any focal length setting.

In manual exposure mode the advantage of a constant aperture lens is even more obvious. If you set the 70-300mm f/4-5.6 lens at f/4 with a shutter time of 1/250 second at 70mm, when you zoom in to 300mm, the aperture will be forced to change f/5.6, but the shutter time will not be automatically compensated and will remain at 1/250 instead of lengthening to 1/125 to preserve the same exposure value.