some confusion about paper

[SoulProficiency]

1.p-lidar-v1 contains mono and stereo method,why p-lidar-v2 dont take mono into consider anymore?is the accuracy of p-lidar-series depened on depth estimation？
2.we found the depth estimation comes from the SDN, what is the difference between SDN depth estimation and stereo camera result(some stereo cameras (e.g. zed camera)can get depth map directly by using camera API).
3.if mono depth estimation has significant improvement(depth anything model), can pl++ use mono estimation to get pl data?