DEM and geoprocessing limits

[JamesTurner2]

Odd question here. I am trying to use the Derive Stream as Line GP Tool. When I add the image service to my map and then select that as the Input Surface Raster, I get Error 001491: ...Cannot process above size limits. If I take that same image service and save as a layer file, and then select the .lyrx file as the input surface raster using the browse button, I do not get Error 001491 and the tool runs without error. What is going on in the background, the data source is the same, so it should be restricted by the same size limit, yet it does not appear to be doing that! I am very confused - maybe it is best to just be happy that it works and move on!

[DanPatterson]

001491: Unable to construct the image service instance.—ArcGIS Pro | Documentation

The caching service failed to start the image service instance for caching.

Analysis cannot be run on an image service input that has the allowAnalysis property set to False.

There is further information on what to do.

[JamesTurner2]

Perhaps that is a different version of 001491, I am seeing "Cannot process above the size limits of the image service." I recognize that there are workarounds for this, I am more curious why saving a .lyrx seems to circumvent the issue if it truly is a limit of the image service.