The relatively modest HbA1c reduction of 0.9% means there's still much room for improvement in the protocol.
Remember many people were on large inslin doses etc, and this is a reduction alongside most people coming of inslin etc. We are used to seeing results from people who take action shortly after finding out they have DM2, most people in the study have had DM2 for a long time.
Also the study is likely to have excluded anyone who had already found out about LCHF themselfs, hence like most studies, the people with the greatest motivation are excluded.