It isn't deep enough for a true dished nest so the hen can support herself above the eggs. She ends up resting directly on them and they break. I remember
@Shadrach posting about this previously. For my DC broodies that hatched, I put them in my broodie house, which has deeper nest boxes (they were fine with the move). In those nest boxes, I put a box with about 3" of slightly damp sand, made a 'dished' nest), then put straw on top....then moved their eggs then moved them. Worked wonderful. Then hens feet/legs were on the higher, supportive edge of sand with the eggs lower, so the hens weight didn't break them, but the hen could still make contact to keep the eggs warm.
These aren't deep enough for that.
Plus, these hens get booted by some of my more dominant (personality& heirarchy wise) hens...