Do you have a source, I've never heard that tbh and even still, TN still has Nioh and NG as part of their game line ups even if they aren't exactly original
If it was developed by Team NINJA which is a sub company under Koei Tecmo, it's an original product by Team NINJA under the Koei Tecmo and Sony publishing brand, including Sony's back up for funding the game.
I read the wiki yeah. Though i'm starting to think you are still not understanding it even from the wiki. The wiki tells you it in itself.
Also Dissidia is an original title yes, including the others. However that game is free lance work. You develop the game for another company. Are you by chance confusing Nioh as 3rd party? Nioh is actual household work from TN, hence original.