Those with that opinion say the sound from that pickup is compromised as it's not right under the 24-fret harmonic. I am not sure I agree - the modern Ricks have had 24 frets for years, and the neck pickup on my 360 sounds great. Interested to know if JH has ever weighed in on the issue.
You show your intelligence by not agreeing!
It should be obvious that locating the pickup under an open string harmonic point only affects open string notes. Just as soon as you fret, the harmonic moves to another spot entirely. Whether that open string harmonic affect is desirable is simply a matter of personal taste; some feel the fundamental is compromised while other like to hear more of the octave overtones.
One thing is for sure- no matter where the pickup is placed, it's bound to emphasize some kind of harmonic on some notes or strings, so the best rule of thumb is to simply place it where it sounds best.