Enclave is a 5000 pound car, and buick has good reputation of safety.
Don't trust the so called crash test rating, even corolla and civic get a lot of Gs, it doesn't mean that corolla and civic are equally safe as Enclave.
In my opinion, the crash test rating is just a 遮羞布 for such cars that have good rating but don't stand much chance in real a crash, some buyers are happy with the rating because it makes them feel safe.