To say if it's pre ignition or not you would need to see both pistons so you can see the state of the other one,
What pistons are they if they are JE these are very strong and will take being touched by the valve, I've had a few valves touching the piston,
You might want to examine the crank to see if this has spread and caused the piston to go in an odd way as its not a hole to speak of the top of the piston is missing on the exhaust side, if it was ignition I would expect it to blow a small hole in the piston where yours looks like it's almost ripped the top off of it, unless there's no oil in the engine, but you can see oil on it so I doubt that