To add to my thinking that Dialga and Palkia GX are in, I have noticed this on the official webpages of each set:
Burning Shadows: 12 new Pokemon GX
Crimson Invasion: 8 new Pokemon GX
Ultra Prism: 10 Pokemon GX
Forbidden Light: 8 new Pokemon GX
I trust you can see the difference, and it explains why Burning Shadows' count did not include Tapu Bulu and Lycanroc while Ultra Prism's count did include them all. Forbidden Light says "new" so therefore Lucario should be excluded from the count.
Annoyingly though, this page here (
https://www.pokemon.com/us/pokemon-tcg/trading-card-expansions/) also contains the expansion info, and for Forbidden Light it just says "8 Pokemon GX" (only this one contradicts - the rest still match up). I'm going to treat this one as an oversight...