Walker started the move - reminiscent of the way American sports stars who took a knee during anthem playing - before the February match between the Indigenous and Maori All Stars in Melbourne.
The SMH reported Addo-Carr wants a national conversation to address the absence of Indigenous reference in the anthem.
"I've forgotten how to sing it. I haven't been to school in about 10 years. I hardly sing it anyway," he said.
"I am a proud Australian man but a proud Indigenous man, too. If it's not going to stand for my people, why should I sing it?"
Walker has reconfirmed his stand, one that retired superstar Johnathan Thurston received a surprising lack of discussion.
Game one in Brisbane is played on Wednesday.