You make it sound so simple

What happens if you're weaving through a valley at high speed, suffer an uncontained engine failure disabling the FCS making it impossible to gain altitude.
You may as well ask, "what happens if the wing falls off"? It's always possible to make any problem hard enough for it to be beyond handling. If the FCS instantly fails, you're most likely a mark on the treeline. Otherwise, ROLL, PULL, is in every fast jet pilot's instant reaction list.....
My point is that your scenario is less likely and probably less dangerous, than straight and level, very fast, at low level. Valley running is not done at high speed. It's most likely being done at 'corner velocity', or close to it. You can't turn worth a damn at high speed. In numbers, that's probably 360 to 420 kias...uncomfortable, but survivable ejection territory.
The only advantage I see in engine troubles occurring in a Rhino over a PC9 would be the two engines. A Rhino at MAX power is more than capable of sustaining flight, depending on fuel, payload and other systems remaining viable of course.
Two engines is a rather big advantage, and most likely explains the very low attrition rate of our F18s compared to the Mirage. But, you won't need anything like max power...and anyway, external stores are gone...literally at the flick of a switch.
Given the obvious difference in flight envelope of a PC9 and Rhino, I'd rather have an engine failure and bail out at 200kts than 550kts....
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So would I, but my point was that I did not, and still don't, think you understand why high speed is bad. How about thinking about this phrase (which is, as best I can remember it from a USN accident report..in which the crew survived)...the ejection resulted in the displacement of some internal organs to outside of the body.......
Speed to height sounds simple. It is simple. And it is the solution that every knuck in the world will try to achieve. Eject at as slow as speed, and as high, as possible.
A lesson they would never forget in the context of the PC9's principle role being a trainer - I assumed the crew were student and instructor. A comment made prior to seeing the photo.
As East Sale does no ab initio pilot training, and is the home of the Central Flying School, I'd expect that the student was a fully qualified pilot who was undergoing the RAAF instructors' course. So yes, he's student, but not in the sense that you normally think of.