Average movecount: 13.5
Average double turns: 1.4
The eight cases can be categorised into cases with 0 blocks (2 cases), 1 block (4 cases), and 2 blocks (2 cases).
The cases with no block are either a pure twist, which has a zigzag pattern of a colour in front and back (blue and green in the image), and the other case is 2 sune algorithms separated by a U.
The cases with two blocks are also 2 sune algorithms separated by a U, essentially mirrors of each other depending on whether the front block is on left or on right.
The cases with one block are variants of the usual OLL algorithm for this case, 2 sune algorithms with intermediate moves cancelled. The can be identified by the presence or absence of a zigzag pattern on the side opposite of the block, and the position of the block.
Note, these rules are only to make learning of these cases simpler. For speed, a better recognition system is to be adopted.