It's been well understood for a few decades that the combustion process gets completed faster with a closed chamber.... and that is another aid in avoiding detonation tendencies. As far as the oval shaped 'pocket', that is an interesting observation. You might want to read up on a topic called 'spark kernal'.
You ought to read up on this thread to get a bit of appreciation on how valve shrouding can hurt flow... some of it can't be avoided with a close chamber but at least you'll know not to crowd the valves too closely.
Intro to a port job
