You are telling untruths.
The land program didn't require other documentation because it was "important", or because a COLB isn't proof. It was a program where to be eligibile your ancestors have to be Hawaiian. So documentation about your ancestors are required.
The COLB is valid for any purpose which requires proving the facts of your own birth, but if the question is one of geneology other documents are going to be needed. Typically, you birthers distort this to fit into your own preconceived ideas.
Your ancestors (parents) are on the COLB. Their COLBs have their parents, and so on.
If it were merely a question of ancestry, COLBs would suffice.