What on earth are you talking about do you even know how karin heals herself she bites herself and gives up her lifeforce to heal her injurie. Kabuto is reffering to that ability. Naruto, Nagato, kushina haven't got any such ability take as an example when Madara and Obito ripped out the 9 tails their life force didn't heal them in the slightest. Even in Naruto's case his body was done in torn to shreds. It didn't heal in the slightest. And when kakashi made that statement it was after Naruto already activated the 9 tails power (against Haku).
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Here's kakashi confirming even Naruto's stamina's root is the 9 tails the word he uses is influence. If Naruto doesn't have access to its abilities naturally their wouldn't be any influence.
This is a few chapters after the healing comment by kakashi.
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Here's jiraiya confirming the seal has been set so the kyubi's chakra slips out between the seal and mixes with Naruto's. Now it wasn't Naruto, or Kakashi or the 3rd who set it like that it was the 4th Hokage. So Naruto's always been healed and enhanced by the 9 tails whilst which he got solo'd by Madara.
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Here's Orochimaru confirming that Naruto's and the 9 tails chakra overflows when his emotions are heightened. Nothing over flows if it's not already flowing.
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Here orochimaru confirms the 2 are fusing so he halts the fusion (with his seal) so it's stuck where it is. This fusion resumes when Jiraiya removes the seal.
So like I said your ignoring Mangafacts to prove a point that doesn't exist and give a feat to a character which isn't his own. I rear when kishi makes a statement he wants to covey some thing to us. Kakashi's words are as clarify as day.
In case your wondering about the uzumaki women who heals herself and how she does it.
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She's impaled
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She bites herself it's the same technique she uses to heal others. It uses her lifeforce and shortens it with each use.