yeah, the yonko has not seen each other in decades, kaido has a close call against oden but that's it, iirc bege has said that he saw big mom fight in the short time he worked under her, but it was mostly against fodder cannon balls, nothing so challenging.
forcing a 68 year old yonko to sacrifice her life span against you is an extremely impressive feat.
kaido is still looking way more impressive compared to big mom imo.