> Allwinner chips are lockdown-free even without this - you just need to hold down the right button/pin at poweron and the ROM bootloader goes into a mode that lets you load unsigned code over USB.

Side-loading unsigned 'ROM's/packages and gaining root are orthogonal concepts in Android: sometimes you want to obtain app-level root in the factory-installed OS - sideloading won't help with that (unless you are side-loading a rooted ROM, but that is not a given)