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. This kernel code is simple incompetence.
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)
As I said: sometimes you just want to run 1 app as root, not replace the kernel. Also, good luck getting a usable device with your own kernel/software when chip manufacturers don't provide drivers: unless you don't mind the usual litany of XDA caveats ("N0irROM v.0.4. Not working: Camera, GPS, Hardware acceleration. new: mic now working, randomly reboots less often")