About as much as telling your kid to not drink beer while you are doing it yourself.
Phone addiction is harmful to everyone at all age groups. It's not really the individuals to blame through. The tech companies have broken human psychology and developed something more addictive than drugs.
You’re not going to overdose from using your phone too much, or die from withdrawal if you suddenly stop using your phone, so that seems like a stretch.
The claim is usually made without specific citations. The few studies I'm aware of show correlation between mental health issues and phone use, but don't show which way the causation runs. It's just as plausible that mental health causes more phone use, yet these message boards always like to blame the phone for the mental health issues.
Phone addiction is not identical. In some aspects its similar but in most others not.
U.S. Government info: https://www.nhtsa.gov/risky-driving/distracted-driving
Telling your kid to not drink beer is giving them the courage to say no to drinking beer. I personally don’t just bark out rules with no context. I also have discussions with my kid about why drinking beer can go awry. We all expect that they will, likely before we’d feel it’s relatively safe. So I want him to at least know what’s in store and how to not make compounding mistakes.