They have curves for ischemic heart disease, diabetes, etc. in Appendix 1. The data points are quite noisy but generally there's a clear trend and the J-shaped curves they used seem appropriate. I think given the multi-national nature of the study it's not just a correlation due to social drinkers being richer.

That being said there are still a lot of questions about type of alcohol and drinking patterns. For example https://newsroom.heart.org/news/study-finds-drinking-wine-wi... found wine lowered risk but beer and liquor increased risk.