One thing I like about Slay the Spire is that it explains the consequences of your actions. Maybe folks consider hidden information to be Explorer content, but in a fairly difficult game with permadeath, consistent but limited information comes to “fail and die until you try every option and memorize it” or “read the wiki.”
For example, when you start a run (assuming you made it to the first boss), you get a choice of bonuses, some with tradeoffs. Many roguelikes would have you pick one of four doors with vague descriptions like, “the red door smells of blood and gold.” Slay the Spire just says explicitly, “start with half health and 250 gold.” Similarly, events in Slay the Spire tell you what your choices mean. For example, when an event offers you a choice between a banana, donut, or box, you are told the implications. There is no obvious reason why a banana would heal and a donut would add permanent hit points, so it would be just a blind pick without the info, until you memorized the outcomes of the event. Or read the wiki.
Perhaps what I am getting at is that many games punish you for not reading the wiki, and it seems like bad design to drive players to the wiki rather than putting the relevant information in the game. Yes, you could count that as a spoiler or learning the game, but given that the penalty for failure is starting over from the very beginning, hidden information is closer to Fake Longevity than Explorer content. And I’m saying that as an Explorer; don’t do that for me, I hate it.