[bobthepanda]

The camp in this article is located in Changi, in Singapore. Singapore has always had a large Chinese population (it actually was originally in Malaysia upon that country's independence but got kicked out for being too Chinese). It would be surprising if not a single one was familiar with some Chinese writing.

[CrazyCatDog]

They did, the translator communicates to the prisoners in English, and they pass along in Japanese to the guards. The article says they asked the translator.

[bobthepanda]

They didn’t know the word which is different from not having any knowledge of how Chinese characters are written.

Chinese is not 1:1 with Japanese so that’s not surprising.