Later: if the baby was in NICU (neonatal intensive care unit, care will be different.
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I suggest their experience is what the made it. My daughter gave birth to her 5th baby this summer. She has never taken supplies with her. She was breastfeeding feeding. They suplemented with formula until she was more rested and had more milk. If she needed something she rang the buzzer and got it. Diapers and wipes were in the room. Baby had pacifier available once they got to their room. Perhaps other things had to be asked for so the nurse could know mom knew how to use them. Once the nurse showed my daughter when and how to use the bulb, they left it in the room.
Were they aware that the nurse also took care of other babe's and moms, that they have a plan for doing things, such as bringing in supplies. I was with my daughter as she and baby were wheeled into their room. It took a couple of hours to get settled. 2 or 3 different specialist.came on to see her and talked with nurses about what mom and baby needed. My daughter dozed in between. She was relaxed, glad to have baby in her arms. But then she's experienced this 5 times. Her next youngest is 3. My daughter appreciated them guiding her as she came up to speed again.
Is this her first delivery? Has she been hospitalized before for something else? Often when people are not familiar with hospital routine they get defensive. Perhaps, with an unexpected early delivery they were more sensitive. I know for me, that abrupt changes in plans make me anxious. Anxiety can make people defensive and difficult to work with. When I was young, in a new job, I was difficult. I didn't realize how difficult until years later.
My daughter had a good experience with the hospital. Her husband did not. He expected them to do things his way even when he had no knowledge or experience. When he felt they were ignoring him, he yelled at them. When he got home he ranted for an hour about how incompetent they were. He uses anger to cover his anxiety and fear.. Of course, the nurses avoided him when he went into a rage. They focused on mom and baby.
How people feel about their experience is an individual thing. Some people are sensitive and defensive. They expect a bad experience, their attitude and actions cause a bad experience.
I doubt that your brother and wife were not given what they needed. I suggest 4 bottles is the starting amount. They could ask for more. In my experience, newborns eat very little. If the bottles were 2 oz, that would be 8 oz of formula in 12 hours. That is more than enough for a newborn. The bottles I've seen were 4 oz.
I wonder if their lack of preparation threw them and they didn't know how to accept things in the hospital. It's interesting they claim the hospital didn't give them supplies and they didn't have supplies for themselves. It's common to project on to others our own foibles.
I hope they settle in and enjoy their baby.