But it shows a lot more than vertical speed? I mean the main point is you're being very disingenuous when someone references the HUD on the F1 and you're like "what HUD? The F1 doesn't have one, I have no idea what you're talking about". Because obviously anyone can deduce what component of the aircraft someone is talking about when they're referring to the HUD in an aircraft that has a "sight" that includes a ton of traditional HUD info.
But even beyond that, the HUD in the F1 includes and is not limited to:
Altitude
Heading
Pitch ladder
Bank indicator
Radar range
Time till missile impact
Computer calculated target interception angle
Gunsight and radar assisted pipper
The point of a HUD is a display that lets you have your head "up" instead of "down", and all of this information on the sight was previously relegated to the instrument panel, therefore introducing an improvement on letting your fly with your head "up". Just because the means of projecting the image is optical instead of digital doesn't change the entire function of the display.