The explanatory supplement to the Astronomical Almanac (1992 edition page 477 para 9.211Equinoxes and solstices) defines the time of the equinox as that when the sun’s apparent ecliptic longitude is 0, 90, 180, 270 rather than in terms of declination. I suppose from a geocentric point of view these should be equal but I wonder if it may account for the difference.
Mike