It is possible that it was always proprietary, but Qualcomm has a history of buying up stuff and locking away the documentation for it, so I’ll go ahead and blame them again !
I would like to do a bit of reverse engineering on the firmware when I get some time, I hope they haven’t bothered signing the firmware and that we can just flash our own moded version at some point (but I am not expecting it to be that easy ¯\_(ツ)_/¯)
If I find anything interesting I’ll happily share it here 