Because on the lonsec site they say that they use the...

Because on the lonsec site they say that they use the Approved/Not Approved scale for products that have 'lack of a meaningful peer group (as defined by Lonsec) renders a tiered rating scale less relevant. If a peer group subsequently develops, then Lonsec may adopt a tiered rating scale.'. As there is no peer products i dont think they can use the other system, as evidenced by the fact that they used this rating system over the traditional scale