160 kts or 600 ft in the JP was a hard requirement during my time as an instructor. And the comments about pre-conditioning for deliberate practice are spot on - it makes it much easier. The only time I saw real startle factor was as a student on CFS when the exchange USAF QFI was flying from the left seat and decided to do the take-off as bit of personal handling practice (fair enough). What he wasn't expecting was his student QFI to throw an EFATO at him by closing the throttle once we hit turnback parameters. He just made the runway, but only after a bit of faffing, and he wasn't happy. At all.
We had a short discussion once 'safely' airborne during which he asked me what the hell I thought I was doing. I asked him in return why he thought he would get warning of an engine failure just because he was a waterfront (staff) QFI. He then agreed it had been an interesting experience for him, and I promised not to do it again...
I hope we can hear some facts from the official investigation soon. I also hope some of the excellent advice aired here about the wisdom or otherwise of turnbacks might save a life or two in the future.