www.elitefourum.com/t/a-guide-explaining-why-no-rarity-comes-from-packs-and-decks/16617/1
Here is a thread about the cards if your query is about what they actually are.
I think Scotty is mostly talking about the investment perspective when he says not to get into them. I’d probably agree. The problem is at a certain price and grade, you can get a decent 1st ed base set for a comparable price. Most English-speaking people will naturally opt for the 1st ed set over a no rarity set, so the cards are in a kind of awkward position where despite being hard to find, people don’t want to pay out that much for them since they would rather put the money elsewhere. But there’s nothing wrong with the cards if you like them as a collectable, I have a couple myself.