Ask HN: Why can't you use m3 MacBook Air keyboard with two external displays?
Why do you need to use an external keyboard with the MacBook Air in clamshell mode?
Why can't you just turn off the internal display and use the MacBook Air keyboard?
Why can't you just turn off the internal display and use the MacBook Air keyboard?
But as for why you can’t turn off the display, I suspect you can somehow.
Isn’t that what a Mac Mini is for?
The original commenter was taking a dig at MacBooks, and I'm calling him on it - where does it say that the Pro will operate like this, and do any other laptops do it? Neither of mine seem to, and my work Dell doesn't either as far as I know.
If the lid is closed, you need to use an external keyboard (obviously). If the lid is open, you can choose to use either the built-in keyboard or an external one. No one ever said you couldn't use an external keyboard. The OP wants to use the built-in keyboard but not the built-in screen (i.e. the screen should be off). The commenter seems to think that it's an intentional anti-feature that is only available on the Pro model. I believe that there are no laptops that do this, and I wouldn't personally care to work that way even if they did.
So to answer your specific comment, the user is always free to use the built-in keyboard or an external keyboard. Unless, of course, the lid is closed - then you pretty much have to use an external keyboard.