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This was a meta-analysis, so they couldn't do this unless the studies they were analyzing reported data on that. The paper doesn't mention this issue in its discussion of the findings, so I'd guess it couldn't be used meaningfully. (The paper does mention the issue in a general way as a challenge of assessing the risk of alcohol consumption.)

Not answering your question, but my understanding is that it's well known that this is one of those paradoxical correlations.

Granted I have no source for this other than I feel like I've read it somewhere, but you're definitely not the only one to have this idea.

Could also be that moderate drinking could help you find friends and a mate, both of which decrease mortality.

Exercise, diet and regular checkups are the key to living longer.

It may be that people who are moderate drinkers are more likely to do all or most of the above.