Impaired is impaired. Shouldn’t drive if your ability is compromised, especially when most people only start off with half a clue.
Coffee is also dangerous in the sense that it masks the sensation of fatigue, but you are still impaired. Driving tired is extremely dangerous as well.
Yes, people frequently get it wrong and when they are dismissive about it, they are demonstrating their lack of willingness to educate themselves.
It may seem like semantics to quibble over technical language but if I ask someone to pass me a saucepan, when I want to use a frying pan, then it’s pretty stupid of me, isn’t it?