Strange as it may seem, there are times when splitting from the very beginning of the document is desirable. Example, when I intend to turn an imported document into a container document with all of the parts previously in one file, turned into sections beneath it. I could create a blank container for this imported document, and then split it up from there, but this means extra steps. Any thoughts? Is it too weird?
del
Yes, split documents will not work if the cursor is at the beginning or end of the document. Conceptually, it just makes no sense. It may make sense to you in very specific situations, but for the program, it would be a little odd to allow to split at the beginning of the document - because then you, in fact, not splitting. 
Not to split hairs, cough, but in non-euclidian space, there is no – what you are referring to as – “beginning” or “end” of a document.
They are circular.
Wha? 
Aaarrrrrggggghhhhhh. And lol.