OP has a color printer...? Do you instead mean to say that tracking dots shouldn't be printed in B/W mode?
I doubt that tbh - the wikipedia article above shows Reality Winner got caught printing (presumably) black/white NSA documents because the printer was able to print the color tracking dots.
OP wanted to be able to print in B/W mode when out of color ink. Ostensibly, the tracking dots' purpose was to stop currency counterfeiting, so they were only ever added on color printers (not B/W ones).
Therefore, not being able to display the dots shouldn't be an obstacle to the printer operating in B/W mode, as it would effectively be a B/W printer in that case. The more likely explanation is simply that HP wants to sell more overpriced color ink.
I doubt that tbh - the wikipedia article above shows Reality Winner got caught printing (presumably) black/white NSA documents because the printer was able to print the color tracking dots.