Of course, you’re technically very right - what they see is not vagina.

But in the culture, the word often simply refers to female genitals as a whole.

That doesn’t mean anyone using that word is not aware of the words “labia” and “vulva”, they can even differentiate between labia majora and labia minora etc.

But for the sake of brevity and simplicity, people just say “vagina”, even if it’s not necessarily a technically correct term.

I feel you and what everyone is doing annoys me to, but our only recourse is to do something worse.

My proposal: we start calling our cock “corpora cavernosa”.

Examples:

• “Hey, Chumley, don’t just stand there with your corpora cavernosa in your hand.”
• ”He’s being a total corpora cavernosa!”
• ”My corpora cavernosa got pinched by my zipper.”
• ”Hey, bro, does my corpora cavernosa hook off to the right?”