Is Wulfharth dragonborn? This is killing me

[Daiji]

Was reading the UESP lorepage on Wulfharth and at some points it is stated that he was a dragonborn, but the only reference about him being dragonborn I can find is Balgruuf's dialogue. Meanwhile, The Arcturian Heresy specifically states he isn't dragonborn (sic: "He goes directly to High Hrothgar to hear the Greybeards speak. When they do, Ysmir is blasted to ash again. He is not the chosen one."). I know Wulfharth lore is a whole mess and both sources aren't super reliable, but I got my head stuck on this issue.
Balgruuf is no scholar, so maybe his version of the story shouldn't be taken over the book. He even refer to Tiber Septim as Atmoran, witch is its own can or worms. At the same time a lot of dragonborn lore was only added to the game after Skyrim, so maybe we should have this in mind while reading Arcturian Heresy.
I was sure he wasn't dragonborn, but after trying to get myself a crash course on Wulfharth lore I feel even more confused...

[Redscoper]

he might be he might not there isnt enough evidence to show either way