It appears there is a bug in the orbbec sdk resulting in the orbbec femto mega is unable to achieve the NFOV unbinned 640x576 resolution. Setting the device to 640x576 does change the resolution, but the depth is still binned just upscaled. This can clearly be seen by comparing it to the 320x288 binned NFOV and the 1024x1024 unbinned WFOV.
Here is a depth image of a wooden spoon (in the center).
Left is 640x576 “unbinned”, Middle is 320x288 binned, Right is 1024x1024 unbinned
As you see, while the 320x288 is blurrier from Orbbec viewer, the resolution of depth is the same (seen by most easily by the blockiness of diagonal lines), while with 1024x1024 its clear this is unbinned sensor data.
I own 3 orbbec femto megas, 2 computers and have seen identical behaviour on all devices, including running this directly from the orbbec sdk depth viewer example not the orbbec viewer and testing different resolutions there. These devices also have updated firmware.