That isn't what trace means, though.

This is the data averaged over the tanks: https://www.science.org/doi/10.1126/science.abc1507

The variance in concentrations is massive. The concentrations on average is barely below legal limits and the bioaccumulation factor for these isotopes is fairly sizable in marine life.

Tepco is cutting corners on this release. They have a history of cutting corners and they will continue to cut corners. The cleanup is a massive money sink for the Japanese government and is something they are eager to be rid of (also, y'know, some old people dying is probably good for Japan's demographics). Unfortunately for Japan, they aren't the only people eating fish caught in Japan.