That really is a mystery. I recall my first neurologist looking at my chart and when I brought up the constant bitter taste, he just paused…..then said, yeah….CNS…that’s tough. My second neurologist did diagnose my B12 deficiency, but didn’t say much about the bitter taste. And, the ENT who witnessed my regular sense of smell return says in time it may. He thinks it was covid that attacked me. I have nothing to base my beliefs on except that my neurologist thinks my paresthesia may fully resolve, so why not my taste. And, my ENT encourages me to expect it.