Another thing I noticed is that the model generates prone and side poses more easily if you switch it to a landscape.
Prompts used: sweetie belle (mlp), filly, foal, female, young, solo, two tone hair, white fur, pink hair, purple hair, unicorn horn, unicorn, pony, my little pony, mlp, green eyes, curled hair, cute, on front, spread legs, panties, teats