This issue came up recently after I retagged a pair (1, 2) of questions to add the dwarf-fortress tag. Both of the questions only had the dwarf-fortress-adventure tag.
A while later the changes were reverted and a discussion began in the comments of the first question. My feeling was that questions should have their game-related tag, even if there are relevant sub-tags which would imply it.
They believed that having the one tag removed the need for the other, as people could still look at questions from both tags by using wildcards in their search (e.g. dwarf-fortress*).
I feel that it's unreasonable to expect an arbitrary user, while browsing tags, for example, to assume that the tag for a game wouldn't include all the questions about that game. And other games with subtags can't be wildcarded as conveniently (team-fortress-2 and tf2-pyro).
Additionally, for consistency, only 2 of 21 dwarf-fortress-adventure questions don't also have the dwarf-fortress tag.
So, in essence, do people feel that a question about a specific game should always have that tag, regardless of its other tags? Should those questions in particular have the dwarf-fortress tag added back?
dwarf fortressautocorrects to
[dwarf-fortress], thereby excluding
[dwarf-fortress-adventure]questions. So I agree with you: if the tags aren't going to me merged, then all of the Adventure questions should also have the primary tag added so that people can properly find them when they want all questions about the game in any mode.