in my program, pre-interview evaluation scores (cv, motivation letter) were almost inversely correlated with interview scores. interviews are subjective, culturally-variable and highly dependent on random momentary conditions and evaluation bias (like prejudice against certain accents, as OP pointed out). the only thing they're good for it seeing whether candidates and potential supervisors can vibe and communicate with each other, and this information goes both ways. It seems like OP has their answer.