Clean on board bill of lading & Shipped on board bill of lading?

I was helping my colleague working as an intermediary who got into the following situation.
The buyer who's importing goods by a container wants to stipulate CLEAN ON BOARD BILL OF LADING in the letter of credit while the seller insists on stipulating SHIPPED ON BOARD BILL OF LADING saying that the carrier cannot guarantee the condition of the goods inside the container as he cannot open it. Since we're new to the container transport, we think that the seller's words make sense. The cargo is inside the container and it is to be transported from one port to another.
In spite of hours of research online, I couldn't find the answers to the following questions;
1. If what the seller's saying is right, does it mean that clean on board bill of lading can only be used in the bulk transportation but not in the container transportation?
2. If shipped on board bill of lading is stipulated in the letter of credit, how can the buyer know that the container will be apparently in good condition at the time of loading, and if not(if the letter of credit does not mention "CLEAN"), who should be held responsible for the damage to the cargo?

I hope someone could give an answer as soon as possible because we're stuck here.
Thank you in advance.