From this theory, he taught 3 grown adults then. Because they are 24 years older than Kakashi's generation, thus this makes it look like Kakashi was a baby when Jiraiya, Tsunade, and Orochimaru were like 12 (hence why it looks like some kind of plot hole). Asuma was born when Hiruzen is in his 40's so this wouldn't really help. Tsunade was also 54-55 when Danzo died so take away 31 years and you get 23-24. This most likely correlates when Nawaki died: The Second Ninja War. But this is the First one correct? So this would make Tsunade around her 20's when her grand-uncle dies in battle. I know Hashirama was old enough to see Tsunade as a baby but his brother old enough (and still looks ilke in his prime) to see Tsunade as a young adult? Preposterous.
Short words, big ass plot hole by Kishimoto.