I think the thing that makes it a problem for most people is that they can't memorise them as "once and done" the way Heisig says he did. So as well as the initial time spent looking at the kanji and coming up with a good memorable story/image/mnemonic/etc, most people I think also spend time in an SRS (e.g. anki, or kanjikoohii) reviewing the characters they learnt previously. It's the review time that really stacks up, especially where you have particular characters that you have trouble with ("leeches").

You could pull it off in the sense of 'I've seen this one before...', but no way do I believe that he learned >60/day with good recall. That'd be like me saying I learned the fundamentals of spoken Japanese in one afternoon. I think it's a kind of bullshit claim to be honest.