database image pose from P_db.m has 0.5m translation difference?

[Grem-Lin]

Hi I am playing with Inloc database image poses and I have a question about pose calculated by P_db.m (please also refer to this discussion).

I found there is a difference (about 0-0.5m in translation and 0-1 deg in rotation) between pose calculated by P_db.m and pose calculated by PnP method (pycolmap) using all 2D points from database image and the corresponding aligned 3D points. I build 3D points by referring hloc and I used the camera intrinsic of "SIMPLE_PINHOLE, 1600, 1200, 1385.6, 800, 600" which I believe is correct.
Also, I use aligned 3D points and two poses (one from P_db.m, another from PnP) to render images. I found the rendered image from PnP is more close to original image while rendered image from P_db.m has an obvious shift (I can share the images if necessary).

Do you have any insights of why this happened? I feel translation difference about 0.5m is huge, especially under current Inloc localization threshold: (0.25m, 10°) / (0.5m, 10°) / (1m, 10°). I think pose from P_db.m totally makes sense, but I didn't see anything wrong with pose calculated from PnP.

Thanks!