" Nightmare Amalgam
And hypothetically if it did mean that, would buying them now mean I would get a full refund and have the available in wild?
No, Battleground has nothing to do with Standard or Wild. You don’t craft the cards you can pick in BG.
Oh right these were BG stuff. My bad.
But say it wasn’t? Would it work the way described?
Whenever cards are moved to the Hall of Fame, the announcement specifically mentions it like in these blog posts:
If a card is announced to go to Hall of Fame in the yearly rotation, yes, though you won’t get the refund until the rotation date.
Only except is when they moved Vanish and Mind Blast to Hall of Fame in the middle of an expansion, on much shorter notice. And you didn’t get a dust refund if you already owned the cards, since they were Basic cards