Once again, this could have been done with A9LH, and there have been proof of concepts.
Example: Linux for the 3DS
True, but previously it wasn't possible to load them without chainloading (have a payload that loads another arm9 payload that then loads the kernel) due to payload size limitations. Not to mention it is now possible to have a full custom firmware, including custom FIRMs rather than just a custom ctrnand.