Shhh, shut up, it's clearly a foreshadowing conspiracy that is trying to tell us that Salazzle will get a male form
only avaible through a special event Salandit and it also has a chance of being female
Though I am curious on what makes her case different
-WALL OF TEXT INCOMING-
First major thing is that Salazzle is not one of the "mascots" for Burning Shadows.
They would be Ho-Oh and Necrozma.
Second is that Salazzle isn't even associated with the Japanese equivalent to the Burning Shadows set, which is SM3's 'Did you See The Fighting Rainbow' & 'Darkness that Consumes Light' sets.
Rather, Salazzle-GX is part of the expansion set 'Beyond a New Challenge' that's tied to the previous SM2.
With SM2's ‘Awaiting Islands’ & ‘Alola Moonlight’ sets being the equivalent to
Guardians Rising.
Overall, the transition from Japanese sets to international is a bit weird.
Each set in the international TCG for Sun/Moon (Sun & Moon, Guardians Rising, Burning Shadows, etc.) contains cards from the SM TCG set in Japan
plus the expansion set from the previous SM set, with the first Sun & Moon set being the exception to my knowledge.
Though why Salazzle specifically? Your guess is as good as mine, but I can at least make guesses for why the following WEREN'T picked:
-The cover mascots (Ho-Oh and Necrozma):
Both Ho-Oh and Necrozma were likely decided against because they're tournament illegal Legendaries (and too old in Ho-Oh's case). Notably, both Salazzle and Lycanroc Midnight are promoted as being "battle ready", meaning they have been "optimized" (by their standards) for competitive play.
-The secondary Pokémon on the covers (Charizard and Marshadow):
It's likely because Charizard is too old to promote a new TCG set for Sun/Moon and because Marshadow's a tournament illegal
Mythical....
-Other Pokémon with GX cards in the same expansion as Salazzle:
Machamp: Same as Charizard.
Darkrai: Same as Marshadow.
Tapu Bulu and Tapu Fini: While tournament legal, it would seem the Tapus are too "special" to distribute for the TCG outside of special circumstances such as the Shiny Tapu Koko (which had its OWN TCG promotion).
Lycanroc Midday: The only possible reason I can think of is for the sake of variety since Midnight was used for the last set's distribution.
-Other Pokémon with GX cards in SM3:
Gardevoir and Noivern: See Charizard and Machamp.
Alolan Muk and Golisopod: ....no idea. They could have worked just as easily as Salazzle.
I apologize for you having to read all that.
EDIT: Well ****, the image uploader is borked again. That makes part of my explanation a little less easier to understand....