I see it all the time and I'm not sure who to blame. I constantly see authors getting crappy marketing advice, but I also have to hold them accountable for following it blindly and not seeing that these tactics are annoying and childish.
One year for the 48 Hour Film competition, our team did not fare well in awards, and the judges felt the need to give us one of what we call the Crap Awards, which is sort of like a pity prize. We got "Best Zombies". We had the only zombies in the competition.
This was not something to be proud of. It was something we mentioned with a good-humored laugh and an eyeroll, but if we'd actually taken it seriously in any way, we'd have been laughed right out of the local film industry.
Calling your book a bestseller in a minute genre subdivision is like giving yourself a Crap Award. It's sad.