I understand the logic. However, I have observed a peculiar case in the tile 25GN2_22 of the AHN:
On the upper left image you can see that the highlighted buildings are present in the AHN4, while absent in the AHN3 (upper right image).
But since they were reconstructed in the final model(lower left image), this implies that they indeed have a corresponding footprint in the bag input. You can also see that there are ground points in AHN3 which are in the supposed footprint.
When selecting one of the concerned building instances, the “b3_mutatie_ahn3_ahn4” attribute outputs the value false.