Hi there,
3D point cloud visualisation in ArcGIS Pro is very much optimised in terms of speed.
But, quality of visualisation is sometimes way behind, which may result in some objects or parts of las files as well entire parts (tiles) of las files not being displayed.
ArcScene is still doing a better job in displaying each and every point of a Point Cloud...
Disabeling the Cache in ArcGIS Pro helps in some situations, but not always.
Happy GISing,
Martin