In JS 4.1 API, loading a basic MapView in a non-hosted project (url file:///some/local/folder/index.html) results in the following error(s):
"services.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer/tile/1/0/1:1 GET file://services.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer/tile/1/0/1 net::ERR_FILE_NOT_FOUND"
This problem does not present itself in the 4.0 API.
Steve,
It looks like they are using the protocol that the page is running under. This seems like a bug. You need to report this to esri tech support.