dove the Yonaguni 'monument' myself last winter and I'm more confused now than before

So I finally went. Yonaguni, southernmost Ryukyu island, the underwater terrace thing a diver found in '95 looking for hammerhead spots. Everyone's seen the photos — stacked stepped blocks, supposedly a sunken city ~10,000 yrs old when sea level was lower (Kimura's camp) vs just sandstone weathering……