Even though this was not my Husband's experience I have read other's stories where they tell of the surgeon going in that way to look around at the lymph nodes, nearby organs, and to see if cancer has spread outside the stomach.
Sometimes Stomach cancer can cause what's called "seeding" outside of the stomach that can't be seen on any of the scans (ct,pet,etc). The surgeon told us that it looks like white sesame seeds throughout the gut and they can only see it by actually looking in there.
If your loved ones are eligible for the surgery to remove the stomach and lymph nodes you DO want a surgeon that will remove as many lymph nodes as possible. Studies have shown that there is an improved survival rate when more nodes are removed. In Japan, where Stomach Cancer is common they remove lots of lymph nodes and sometimes surgeons refer to this as the "japanese method".
take care,
Amy