What it means is that non-citizens are not essential to the drug trade. You could stop all border crossings by non-citizens and the same amount of fentanyl would get through.
Combatting drug use with supply interdiction is a policy that we used to call "the war on drugs." It is a failed policy by every possible metric. It is arguably one of the most consequential and profound policy failures in US history. This idea that we can disrupt the supply of drugs by stopping the immigrants is just another (and particularly stupid) version of that same tale.
Here's the truth: overwhelmingly the people responsible for overdose deaths are the people who willingly put that poison into their bodies. Illegal immigrants are not responsible for your friend's death. Now, "responsibility" is the beginning of the story, not the end. A person who drove drunk as a 20 year old, crashed his car into a tree and is now a paraplegic -- well, that person is responsible for his paraplegia. Nobody made him do that. That doesn't mean we should just tell him F U every time he asks for assistance. Part of being an enlightened society is the realization that we all make mistakes, and our lives are better when we can support each other when we do.
I would never sit here and say, "oh, your friend was stupid and killed himself, such a shame." It is still a tragedy. There's almost certainly a longer story behind that death -- one that might involve issues like depression and despair, hopelessness, lack of job options, physical over-exertion leading to dependence on prescription pain killers, and even genetic factors that make people susceptible to addiction. And it's important to tell those stories, and learn from them, and try to make it so that these things happen much more infrequently.
Illegal immigrants are not part of that story. You make your friend's death into a triviality or worse when it's an occasion for you to punch down on migrants instead of learning about what actually caused it.