As I understand it, most developing happens in the first minute. So being in the water for a quarter of that time, it would make sense that there would be some image. I'll bet you would be surprised to see how much of an image there might be after a minute.
I did the OPPOSITE thing yesterday, actually...I use a hot water bath to quickly bring beakers up to temp before pouring them in the Jobo. And yesterday I mixed developer into the just-boiling-a-second-ago water. I COOKED some Acros after 8 miunutes at nearly 200 degrees in the Jobo. And if you're going to cook, there are many cheaper things that Across...filet mignon, for instance.
And in my case, as yours, I was surprised by the results...VERY dense, bulletproof negatives. But still an image and the shadow detail wasn't at all too dense. Extreme proof of zone system + devlopment, I guess.