As I said, slightly underestimating. The first thought I got when I saw the Nine Tails in Susanoo Armor was that I thought of Kurama's power within Naruto. I think that maybe a small amount or a short amount of people more are thinking of the Kurama inside Naruto instead of the Bigger more power Kurama.
Do not forget that Kurama was at its Peak of Power back then. Half of its chakra was not sealed at this time meaning that this Kurama could be much stronger and we might need to wait to see its power against the True Several Thousand Hands Technique, as of now, I think we are all unsure of what this thing can do at the current time.
Do not forget that Kurama was at its Peak of Power back then. Half of its chakra was not sealed at this time meaning that this Kurama could be much stronger and we might need to wait to see its power against the True Several Thousand Hands Technique, as of now, I think we are all unsure of what this thing can do at the current time.