While I can't debate "These studies" without knowing what you're referring to, this specific study provides a clear explanation of the study cohort and there's no sign that anyone was excluded or otherwise cherry-picked.
I've found that digging deeper into studies in the past that they would leave out people with heart conditions (specifically with caffeine studies) and not state that _anywhere_ in documentation. And this only came out from investigations.
I have a friend who does statistical analysis for a living, and we have a game where he points out the flaws that are only obvious to those that know statistics and research well, and us laymen are oblivious.
A medical doctor once told me "coffee must be good for you because I drink it!". It seems common that people just want science to agree with them, and they don't care how or why.
I can't prove my point on this article (not enough time/energy/will) but I have watched health articles for years and you can go back to news sites and find this same exact study done over and over, reported in news organizations as if it's new every time.
One stupid example, articles from just CNN going back to 2010 just on one page of search results:
https://duckduckgo.com/?t=ffsb&q=site%3Acnn.com+coffee+good+...
Edit: by "these studies", I mean caffeine, cigarettes/smoking, alcohol, coffee and generally any food or "health" study. If you don't know the exact make up of the test group, then I just assume it's rigged to get a certain result.