I have Oven Spring Envy. I admit it.
It is rare that I get that huge, head back, laughing face on my bread, more of a gentle smile. I see a lot of loaves where the top layer is peeled back all the way to the top with the bulge of risen bread forming a basketball.
What I am wondering whether it is an issue of too much or too little surface tension during shaping?
The rest of my method is fairly typical - autolyse, several stretches and folds, bulk ferment to about 50%, pre-shape, final shape,. overnight cool ferment, 500-450 two-stage baking in sealed cast iron cooker, etc.
That loaf is nothing to scoff at! It looks beautiful.
But I understand what you’re after. Have you tried bulk fermenting to 30-40%? If that doesn’t help, I would try strengthening your starter. There is a thread a few posts down called “sourdough in cold temperature”. There are before and after pics of what happened when I spent a week strengthening my starter. There are also two YouTube links to videos that might be helpful.
Hope this helps!
Will bloom more than a round boule.