This is also true. I remember Chubblot talking about how much better they were getting better at hiding stuff. they have hidden a lot of Minsc's stuff from the beginning (but strangely never all of it) But on the other hand, why would Helia be so much more completely, so as to be erased from the mtg product, missing from the datamines etc. She's a wholey new character, not a returning celebrity like Minsc, not some established fan favorite from the novels or anything. It just doesn't make much sense to hide her, of all the characters.
Everyone already know Minsc, he is the most recognised face of Baldur's Gate after all. It isn't a surprise he would be used to promote products even at that stage. We already know Karlach appearance, race, class, backstory and that she will be a future companion through her dialogues. The genie is already out so might as well add her too. Helia is a still mystery for all except some rare people who are invested in datamined content.
Only question is if she planned to be in why has she not a card, are magic going to release more cards when bg3 is released?
This is one of the reasons im worried we wont get more companions
She most likely doesn't have a card because why would you include a character that hasn't appeared once officially? People would be quite confused by that random character among all the familiar faces.
Wasnt Karlach a random bg3 character? according to her wiki her only appearances are in bg3 and magic. And when the cards came out she wasnt in the game yet
