If you are flying at 100m AGL and the camera is pointing at -80deg, ie 10° off nadir, then the centre of the image will shift by over 17 metres. The default gps_accuracy in WebODM is 10metres.
Should the gps_accuracy number be increased for situations where the centre of the images differs from the drone position by more than the default?
Positional accuracy applies to the camera position, not to the full pose graph, which includes pitch, roll, and yaw estimates, so: if your GPS Z DOP is less than or equal to 10m, 10m is a fine estimate.