It was after the time of Shiragi (ancient Korean kingdom) that people from the Korean Peninsula started to use Chinese-style one-character family names and it is not likely that people from Kudara at that time used the family name Wan.
朝鮮半島の人間が中国風の一字姓を名乗りはじめるのは新羅以降の風習で、当時の百済の人間が王姓を名乗っているとは考えにくい。