In Orthographic mode, can't scale with S, "Orthographic scale" doesn't change length of camera.
The orthographic camera doesn't have scaling data.
While using a perpective camera when you change the scale, it atleast changes the display size. But it doesn't actually change the scale of the camera. If you click Ctrl+A to apply scale. You will get and error which says
Objects have no data to transform. And even though it does change the display size in the viewport, it actually doesn't change the Viewport Display Size property in the Object Data Properties.
While using an orthographic camera the situation kinda worsens. If you change the Viewport Display Size of the camera, the size of the camera can sort of only be increased or decreased as if it were scaled on its local z-axis. If you want to change the display size of the camera, you will have to change the actual Orthographic Scale property of the camera. This is just not possible as it changes the entire thing and it's not just a display thing anymore but rather actual change to the actual properties of the camera.
If I understand it correctly, try imagining the displayed rectangle of the camera and extrude it. Whatever is contained in this cuboidal region is displayed in the camera. In the case of the perspective camera it's more of a trapezoid thing with circular distortion that gets extruded. So for the orthographic it actually makes a lot of sense to see the actual Orthographic scale of the camera in the viewport. It's just that sometimes it's a little inconvinient to see a giant rectangle floating in our scene.