RNA is transcribed from DNA, possibly spliced and exported to the cytoplasm - fine - but its bases can also be modified, edited, and not all such modifications are visible by Sanger sequencing methods and its derivatives.

The Nanopore measures potentials, and if the bases have a different shape then this is measured - not necessarily in an interpretable manner, something must be left for mass spectrometry, but one may be pointed to a difference. And maybe one can even statistically associate such differences with a molecular or clinical phenotype.