16 bit in Photoshop, it's fake?

Hello friends, there is something that has been confusing my mind.

When I create a 16-bit file in Photoshop, all the color and light adjustments continue to act with just 256 passes.

If I create an 8-bit file of 256x256 pixels and pass a white to black gradient I can measure each pixel with its specific depth.

But if I create a 16-bit file with 1000x1000 pixels and pass the gradient from white to black, it's impossible to measure the colors, since all tools continue to work at 256 levels only.

Is there any explanation for this?