I think you expect too much from the VCOM values.
Take a photo of what the screen looks like when reading, maybe everything is OK with you.)
I swapped SD cards on many devices and did not notice much difference. It is very rare that the font looks paler.
I have prepared an image for you from 4A2 from such a device (there are others):
https://ibb.co/SwvB6KS3
https://ibb.co/Y4gbzWwp
https://ibb.co/XfCqGzzW
4C1 I have only three devices, tell me from which one should I create an image:
https://ibb.co/4nKPzL2C