I think the major reason they only ban the Game Sync ID is to give cheaters a second chance to play legitimately.
Especially since this line is a thing:
I've received a ban in Gen 6 PGL, inquired customer support about it, and they told me to make a new game and continue playing legitimately.
Banned again in this recent wave, noticed a particular Pikachu wearing a cap in my boxes wondering how the hell it got there. Or a shiny Tapu Koko wonder card tripped it.