to the best of my knowledge, you are correct on all counts. the new rotary used as a generator does also have direct injection, but i don't think they gain much compression ratio from that, for the reasons you stated. it's more for efficiency. without reading up on it, i believe the combustion chamber mixture and flame front propagation is not great in a rotary (hence RX8 has 2 plugs per chamber, leading and trailing) and DI should improve on it.