No, the printer may use CMYK (or cCmMyYkK inks), but the signals that go to the driver have to be RGB.
In fact, if I remeber what Chris said about PS7, even if your image is CMYK, photoshop is going to convert it to RGB when you print, behind the scenes, because PS knows that you’re printer is expecting RGB data. So in a way, it doesn’t matter, I don’t think.
Yep, that still applies.
It matters because your printer CMYK inks may have a much larger gamut than the printing profile you convert to, and you lose color accuracy and range.
"Some people" are responsible for a lost of false information.
This is one of the commonest misconceptions about printing on an inkjet.