Digital BW, The Print

It seems there are a number of ways to get a BW image from color. I'm
aware of most of them, and am not asking HOW to do it.

In Photoshop you can create a true grayscale image which drops all RGB
channels and has only a 'gray' (luminance?) channel. In Lightroom, you
can create a grayscale image, but it appears to retain the RGB
channels. Other techniques also use the RGB channels as filters to
create a BW image (Lots of controls in the color channels).

The question is: For =good= BW printwork, should the final image sent
to the printer be a TRUE, single-channel grayscale image, with no RGB
info? I like working in Lightroom, but I would need to take the image
to PS to make it a singe-channel true (by my def) grayscale image. Is
this worth doing? Or will the printer/QTR figure it out?

I'm setting up a Epson 1400/QTR/Piezo printer, and they indicate you
should only print grayscale. So I'm looking for clear definition of
grayscale. 

Clear (gray?) as mud??

=Alan R.