Perhaps it's inertia from A23 days? The Fortress used to be the ultimate building you'd build to access some of your civ's best units/unique techs.
In A24, it got demoted to a strong defensive building, but some things remained.
I don't think we should change anything, though. WTF is a very strong tech that needs to be hard to get. Unique techs for some civs (like Mace, Han and Romans) make sense in a Fortress, as they are also very strong. Heroes can also turn the tide in a battle. Seleucid heroes being trainable from CC is just a civilization advantage.