I assumed it was corrected data for KIAS, TAS seems more likely now you mention it. Would've been handy if the report had made it a little clearer.
The report doesn't define "Derived Airspeed" at all, which frankly is a novice mistake. I agree that I think its meant to be KTAS. However, it makes no sense.
1. According to the prelim & final report the Bankstown METAR was 340 deg @ 4 kts and the METAR for Richmond was calm. However at the final fix 6nm from YSBK at 500 ft they are using an 11 knot tailwind component.
2. No met data for winds aloft has been tabled. The Prelim report quotes speed as Groundspeed derived from TXP returns. There are not many data points that correlate between the 2 reports, but there are 9. Just before TOC over Richmond flying pretty much North, the ATSB calculations show a 19 kt tailwind. 4 minutes later having turned through slightly more than 180 degrees at the same altitude (after having climbed further, then descended) they are using a 16 kt tailwind. How does this work?
I don't think any of the "derived airspeeds"can be relied upon at all. Which completely undermines their conclusion that the pilot was not managing airspeed.
This is a seriously flawed report