The median of the parallax is computed in each HEALPix pixel and presented in Figure 14.40 in the magnitude bin. The median parallaxes are generally in very good agreement between Gaia DR3 and GOG20. There are however a few places where the difference is significant, close to the Galactic centre or the Galactic plane (in particular at intermediate magnitudes). The Magellanic Clouds also appear since they are not generated by the model and what we see is the difference between the median parallax in the Magellanic Clouds (of the order of 0.02) and the median parallax of field stars in the same region (which depends on magnitude, see Figure 14.41).
Figure 14.41 shows the median parallax over the whole sky per magnitude bin, for Gaia DR3, Gaia DR2, and GOG20.
There is a systematic difference which, in absolute value, depends on magnitude, and is quite high at bright magnitudes, more than 1 mas.
This systematic is a bit reduced compared to Gaia DR2. At the difference goes below 0.1.
Summary of the results:
The median parallaxes are generally in very good agreement between Gaia DR3 and the model.
There is a systematic difference which is quite high at bright magnitudes, but is reduced compared to Gaia DR2.