There are a few gray areas regarding certain types of dolls and tags. The general consensus is that the "BJD" tag specifically refers to dolls that have rounded, ball joints, and occasionally Dollfie Dreams- essentially those dolls deemed on-topic for DoA. Monster Highs, Obitsus, Pullips, and other such dolls are not technically ball jointed. They have a hinge and peg system, so they're generally frowned upon when tagged as "BJD". That does not mean the dolls are bad. It doesn't mean those dolls aren't good enough to be BJD. It simply means that it doesn't fit the community language for what constitutes a BJD. This jargon is important for people to be able to find those things they want to see and avoid those that they don't. If you do choose to tag one of those dolls as BJD, please be considerate and tag it additionally with the "correct" tags, so that people who don't want to see those types of dolls can block them.