It's probably an attempt at a larger scale extension of what card shops have been doing much more recently (at least in my area) of including varied collection options, i.e. comics and cards.
The standout phrase was the term "variant" as a selling point to the idea.
“Aslan didn't tell Pole what would happen. He only told her what to do. That fellow will be the death of us once he's up, I shouldn't wonder. But that doesn't let us off following the signs.” - Puddleglum in The Silver Chair by C. S. Lewis