We did not see Gai performing Reverse Lotus either but we know he can, Hiashi had less paneltime but last time we saw he was making a Bijuu sized Airpalm while Neji's was much smaller, was capable of doing kaiten and 8 triagrams 64 palms is something passed down in main branch, he has more chances of having capabilities to do so plus nothing indicates he is slow. This is like saying 3rd kazekage is an idiot below Akamaru cause we only saw him as a puppet and has No intelligence feats or first mizukage is Karin level since we never saw him fight.
Tier lists is something we made up, not Kishi. "Above high jounin = low kage" is a mere assumption and naming in our part. Also it is not far fetched to say he can be low kage level.
I think Neji is a capable jounin who is on par/above/can compete with likes of Zabuza, Part 1 Kakashi, Part 1 Kabuto, Asuma, Kankuro, Temari, Darui, Chiyo etc. And Hiashi is above him.
Sorry for talking about Hyuugas this much i know you hate them just for clearing things out.