As you pointed out, the difference between Pokmon EX and Pokmon GX is that the former ones are always Basic whereas the latter ones are always the stage they are supposed to be [1] (except for Tag Team GX cards which are also always Basic)
Xerneas 2021 Pokmon Celebrations rare holo 012/025
In fact, its not hard to have the sleeves and deck box for the cards cost more than the actual cards themselves
Of course, this could all be coincidental, but it is an amusing coincidence nonetheless
(2) At the end of the Battle Phase, if your K9 monster battled this turn: You can Set this card from your GY
Where Generations fits in the era Generations launched on February 22, 2016, as part of Pokemon's massive 20th anniversary celebration that included the mobile game Pokemon GO (July 2016), a Super Bowl commercial, and monthly Mythical Pokemon distributions across all active Pokemon video games