There are many varieties of rice, suitable for different purposes. Most people are familiar with eating rice, but this is not appropriate for sake production.
“Sake rice” is a general term for rice which is suitable for sake production. However, the more detailed “sake specific rice” (included in “sake rice”) requires registration in the local prefecture where it is developed, grown and used.
Sake rice can then be listed as a “recommended variety” locally and local prefectures must supply the rice seed to farmers.
By way of comparison, wine industry grape stock and scions are owned by private companies and grafted on the request of wineries. That means there is no public approval for grape varieties. Contrary to grape stock, rice varieties are guaranteed by public institutes and are required to be available to farmers. Therefore each prefecture has an interest in which rice varieties are listed as a “recommended variety”, because of the consequent obligation to supply the seed to farmers on request.