How about you stop selective reading and say the whole thing. He said Indra inherited his strong chakra not stamina like his brother Ashura.According to Hogaromo Indra inherited the genes therefore the body. No mention of Ashura inheriting stamina by Hogaromo who do we trust Tobi or Hogaromo? As for Naruto he didn't his power stems from him being kyubi host it grants him chakra reserves, stamina, healing factor, faster recovery. Chakra is a by product of spiritual energy and stamina so your point is mute. If the seal gives him chakra being yang hand it would be physical energy and stamina.
Also I trust kishi's word, which is both Tobi and Hagoromoo which neither of their words contradicted each other. Hagoromoo said the very same thing.
As for chakra it is the mixing of both spiritual energy and physical energy together making your speculation invalid. Chakra is not stamina.