Ann: FY18 Half Year Results Announcement Date, page-29

They will only not invoice the customer in cases where the case fails to succeed. You are right that there is some amount of subjectivity to estimating which cases will succeed and which will fail.

The business has in the last few years received a painful lesson from over optimism which results in a writeoff and massive hit to the shareprice. As such Shine has tightened up it's rules around accounting for WIP. Recent accounting changes (AASB15) also impact this.
Bear in mind CEO is a majority shareholder.

Note that Operating Cash-flow is consistently positive. The recent increases in debt relate to funding acquisitions. Due to suppressed share price in the last few years they have not been able to fund acquisitions from issue of equity.