I've never used a 4033, but I wonder if it sounds hollow in the midrange because so many mics (especially the current generation on large-diaphragm condensers) have a prominent peak in that region. Mics designed primarily for vocal use (from the humble SM-57 all the way up to U87's) often have a midrange peak because that's the frequency region where the voice (male or female, really) produces sounds. Some also have a bit of a peak in the upper mids or lower highs to capture the formants necessary to understanding vowels. So if the 4033 really is as flat as it claims to be, maybe its mids sound hollow by comparison with the hyped mids we've all grown accustomed to.
P.S.: FWIW, I tend to favor a more neutral frequency response, so maybe I'll be checking out the 4033!