Support for async reprojection

I’m not sure if I understand how disabeling interleaved reprojection helps with optimizing the performance. Could you explain this a bit more?

If you’re targeting 90 FPS and you’re in situation where your hardware can only achieve 80 FPS then you’d still have to reproject every second frame, because frames simply take longer than the 11.1 ms / frame? Or how is this handled without interleaved reprojection?