Hiruzen was the Professor, meaning that he knew ALL of Konoha's ninjutsu. Like you said, Kishi's word. This implies that Hiruzen had knowledge of most, if not all, elemental techniques, which also begets a certain level of mastery.
I'm not arguing against what Kishi said. In fact, me being a Hirizen fan has always had me realizing that feats are just as important as hype. Nagato has never shown his supposed mastery of the elements, but I believe it was so because of Jiraiya's statements.
If anything, the two have equal abilities in the elements. Hiruzen's ability to master them all exceeds Nagato's due to his non reliance on an aid such as the Rinnegan...
Knowing an element is not the same as knowing all justu for thus said element.
That is the difference betwenn hirzen and the nature of the rinnegan which helps you master all 5 regular chakra natures.
The feat in itself to learn all natures is astounding i am just saying he did not master them all,it was never stated and to assume that somehow knowing an element means you know all justu for that element is absurd and i won't even begin to discuss why that makes no sense.
Hiruzen was also called The Professor due to his mastery of all forms of shinobi combat and his vast knowledge of techniques in general.
He did not learn every justu he knew of every justu.
You can't learn secret techniques or kekegenkai either so if people can't differentiate between Know and Learn then i don't know what else i can say anymore.
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True,which is why i called it an impressive feat its something that took nagato the sages eyes to do when hiruzen did it will talent.
I specifically say this in my first post
