The next paragraph adds the explanation, why its wood is edible:

Although most wood is indigestible to humans due to the high lignin content, the yacaratiá tree is only around 10% cellulose while the rest is mostly water with very little lignin content. Unlike most plants, cells of this tree contain large spaces within their walls which store water.

It is in the Caricaceae (Papaya family) and apparently a pioneer species just like papaya trees. No wonder it is mostly water and hardly any lignin!