The breaking of blocks attached to opened faces of shulker boxes is inconsistent between torches and item frames.
On a shulker box place directly on the ground (with opening face on top) with blocks attached to all 4 sides + top :
- torches : possible on 4 sides + top
- item frame: possible on 4 sides + top
- torches : breaks on all 4 sides + top
- item frame: breaks only on top
Item frames would drop when shulker boxes are opened.