Unfortunatly honor6a vignetting isn’t yet in lensfun official db you can find the xml.
I attached also the image i took for vignetting profiling (i have tried also to use it for flat field, but didn’t worked fine… - here the tryout: Night picture with a phone - #13 by ggc )
The color cast when using flat field file for vignetting correction most likely is caused by some special pixels (maybe pdaf, don’t know). Have a look at this screenshot which clearly shows a pattern of brighter blue pixels.
I had a look at your dng from the Huawei. It seems there is opcode 9 (GainMap), which can be used for flat field correction. I’ll have a look how that can be used…