Wow, does look like they've been managed to form into those curves by weighing down a side limb and then letting it grow upwards again.
Most of them have then had the main trunk removed to make the curved one the primary timber, you can see one that still has its main trunk attached.
Chances are it was a deliberate order from a carpenter to the woodsman that was never harvested due to the war coming along or the introduction of a new material to do whatever job they were intended for.
Most of our managed woodlands fell into disuse when plastics came along, coal replaced firewood & it became cheaper to import rainforest timber.