Perimeter insulation 24mm advantage?

Do you want to leave it out or what? I think the image clearly shows why uninsulated corners are critical..

Yes, I want to omit them.

But you can see that despite the insulation, there are no differences in temperature to be observed, precisely because the masonry so far outside is still very cold.

You can't judge that based on the picture. I suspect you are building monolithically without ETICS. However, the picture shows, for example, a wall structure with ETICS. Omitting the ground slab insulation already has the potential to become a problem.

Your specific question can be answered by the person who calculates the energy saving regulation proof. Only this person knows the exact conditions and can assess the entire system.