Going back to the original structure determination papers for maitotoxin (Yasumoto, Kishi; 1993, 1994, 1996), I find that some of the NOE assignments are kind of fuzzy, because the spectrum was naturally incredibly crowded in the disputed region. Regular 2D NOESY produced a smatter of fizz.
(Reference DOI: 10.1039/a901979k)
So they resorted to a fancier technique, PFG 3D NOESY, to pick out the cross peaks. The third axis in this NOESY is the C13 shifts, so that the protons are also separated on the basis of C13 shifts which differ more than proton chemical shifts (although still not by much, 3-4 ppm in some cases).
If I were asked if I believe in the assignments and the NOE correlations, I would probably say yes, but mainly on the basis of a process of elimination, and not on the basis of unambiguous confidence. But then I guess such is the nature of painstaking NMR structure determination of such complex natural products.
In any case, Spencer, Gallimore, and Nicolaou are definitely on to something, as described in the post before the last one, and we may learn something quite interesting about the NMR data or the biosynthesis.