Do we lose durability guarantee when using disk bufer?

[ruskaof]

The documentation states that when using acknowledgements with a disk buffer, the source receives an acknowledgement only after an event has been persisted to the buffer. However, it also mentions that data in the buffer is flushed (synchronized) to disk every 500 ms. Does this mean it's still possible to lose acknowledged events if the Vector process crashes before the buffered data is fully synced to persistent storage?