Photos Albums reorder images?

Photos is driving me crazy.

When I select a group of images from my Photo Stream in a particular order (also their date-time sequence) and move them to an Album, Photos reorders the images with no apparent algorithm. This renders the Album a useless mismach of unordered images, more like a Photos Pile than like a Photos Album.

Am I doing something wrong, or is this just a crazy Apple bug? I cannot figure out how this could ever pass any quality assurance testing.