FortressCraft...Honestly?

He said he named it Fortresscraft because he wanted to combine Minecraft with Dwarf Fortress. And Dwarf Fortress was the main inspiration behind Minecraft, so he's combining Dwarf Fortress with Dwarf Fortress.

He's just trying to find loopholes to justify his actions. In reality though, this game has everything minecraft has, but nothing that minecraft doesn't have (outside characters and different skins). It does not matter whether he "started to plan this game" before minecraft, because obviously he couldn't pull off a notch and come up with all those good ideas.

He's a thief. Just watch, the new updates will all be just the updates MC gets, I don't think he will be able to come up with actual own ideas.