Word counts for genres

How can a novel be shorter than a novella? If it's a middle grade novel.

I wonder what adding "cozy" to any of these genres does to the word count?

Don't you feel like these days, you can go shorter? I mean, you can't go longer, but you can go shorter.
And for Middle Grade, lots of books are longer than 50k. Mine come in at 60-65k, and that's pretty normal these days for upper MG fantasy. Then, of course, there's a huge difference between lower MG and upper MG...