They are using KIDNEY cells for goodness sake.
A good empirical scientist would surely try taste buds and olfactory cells (flavors include odors that are sensed from the contents of the mouth); and any flavor chemist knows there are greatly disparate things that still taste much the same — a kidney is tuned to just getting rid of the stuff in the urine.
They’re using cells harvested FORTY YEARS AGO for goodness sake.
Why should they go trying new cells when this chain gives consistent results? These cells are already there and wound up industry standard. Probably because nobody had bothered to harvest tastebuds, but since in the end they’re looking for bio-electric reaction it really doesn’t matter. You don’t care if the cells enjoy it, you just care if they react.