Seems like most of yall didn’t read it, but in summary, they concluded what you’ve probably already guessed:

“It’s not about the food, timing, or setting; it’s the parent-child relationship and interactions it helps cultivate that matter.”

Parents regularly connecting with their child is what reduces substance use risk. Routine family dinners just provide a straightforward framework for that connection.

Also note, they said:

Higher family dinner quality was associated with a 22% to 34% lower prevalence of substance use among adolescents who had either no or low to moderate levels of adverse childhood experiences.

Two takeaways here:

1. “Higher quality” implies a healthier relationship. Obviously you’re going to rate dinner with your family higher if you have a better relationship with them.
2. Family dinners alone aren’t enough to overcome “adverse childhood experiences”, i.e. trauma. It seems potentially protective, but it’s it going to heal deeper issues.

may

They may, and they may not

Don’t think that’s caused by the dinners specifically here.

Or maybe not using drugs will lead you into having more family dinners.

Simultaneous existence of two things doesn’t imply causality let alone the direction of causality.

–Edit–

In a similar fashion there is a strong correlation in my country between people wearing beanies and hip injuries amongst the elderly. I still doubt we should stop wearing beanies in freezing temperatures to protect the hips of grannies.