First, I'd like to completely agree with you. That is horrible.
OTOH, it seems like first-time moms tend to think babies need to be kept warm under any circumstances. My niece was a premie and she came home around 4 pounds. They were told she needed 1 layer more than what we would be comfortable in. Now, it was end of August and about 85 degrees. No, she did not have the baby on the beach, but the baby did have a long-sleeved sleeper and was swaddled in a blanket. I'm usually cool until it hits 80 and I was sweating in shorts and short sleeves. My poor niece kept trying to get out of teh banket. When I was holding her, she tossed and turned until she was free of the blanket. Then she settled down. Pretty obvious to me that she was hot. As she lay there sleeping in my hands, my SIL, just kept looking at me. Finally, my niece hiccupped. My SIL grapped her, said she must be cold and proceded with teh swaddling thing again. Poor thing went back to struggling for freedom and to cool down. If a ~30 yo could be that way. I can see an 18-20 yo doing the thing on the beach.
Does that excuse it? No, but it does seem to me like the hospitals should stress, especially with summer babies, that heat is just as bad, if not worse than cold.
Just my 0.02.