Weird Water Supply Line On/Off

Here is the water line as it comes out of the wall and leads to the toilet in this powder room in Houston.
Usually this line or pipe is accompanied by a faucet handle, which you can turn to either turn on or shut off water to the toilet.
But this is the first time I’ve ever seen this different method of controlling the water flow.
Instead of turning a handle, you pull the small plug and it closes the pipe and shuts off the water.
Or, push the knob in and it will open up the lines and let water flow.
The round silver plate against the wall is decorative for hiding the hole in the wall. This plate is called an escutcheon .