I've got the same question. I'm looking to run it both ways, but when I'm running Snap Pour Points tool for a set of 15 points on a flow accumulation raster, it's hanging. I'm needing to do this because though 13 points which were generated from places along the stream line feature still coincide with the stream line raster cells in the flow accumulation raster, 2 of the points are just off of the stream raster cells and need to be snapped over just a little bit. I'm using ArcMap 10.6 and the Snap Pour Point tool repeated hangs, even when just running it against a single point. Thanks in advance!