I found the documentation on it: https://github.com/GPUOpen-LibrariesAndSDKs/LiquidVR/raw/master/doc/LiquidVR.pdf
It's actually being called Late Data Latch and the whitepaper has a brief explanation:
The Late Data Latch helps applications deal with this problem by continuously storing frequently updated data, such as, real-time head position and orientation matrices, in a fixed-sized constant buffer, organized as a ring buffer. Each new snapshot of data is stored in its own consecutive data slot. The data ring buffer has to be large enough to ensure the buffer will not be overrun and latched data instance will not be overwritten during the time it could be referenced by the GPU. For example, if data is updated every 2ms, a game rendering at 100fps should have more than 50 data slots in the data ring buffer. It is advised to have at least twice the minimum number of slots to avoid data corruption. Just before the data is to be consumed by the GPU, the index to the most up-to-date snapshot of data is latched. The shader could then index into the constant buffer containing the data to find the most recent matrices for rendering.