You can "learn" assembly?
No you can't.
"Assembly" doesn't even exist as any "assembly" is completely chip (and might I say, board dependent) and using it is anyway similar to killing cockroaches by throwing lego bricks at them. While being gimp'd up.
But the assembler (the program) and the editor to write the code can fit into 15 KByte. That's a plus.
Anyone who expresses the desire to "learn" it is on a hiding to nowhere. You can just "do" it, and best print out the PDFs manuals first, because there will be much cursing and flipping through pages.
I also fail to see who would want to use this approach in 2016 even for the IoT unless stuff is being shat out so quickly that there isn't even enough time to wire up a proper compiler backend to generate the binary specific to said "Thing". Go figure.