The problem with confident assertions like this is they are so easily undermined by plausible alternatives. On another thread I commented that many great efforts at secrecy had been compromised by unfathomable slip-ups, and at the same time on the same thread someone posted a perfect illustration of this, of how the founder of Silk Road was caught using his real name in an email address seeking to hire programmers.

When Satoshi first wrote his paper and signed on to this forum, Bitcoin was nothing. Privacy would have been of little issue at first, growing gradually over time. And by then it would be too late. So he could go to great lengths in other ways, but could only hide in plain sight on this point.

I'm not saying that's conclusive, just giving an example of how the various arguments being put forth pro and con are not very strong. Thus my surprise as how confident most people are - and yet one side or the other must be wrong.