You don't have PTSD, and you are right to question this alarmist diagram that suggests this misdiagnosis is common enough to be worth considering by lay people concerned about ADHD symptoms. A more broad application of 'trauma' /might/ be a better fit for this diagram, but PTSD is a very specific diagnosis (most commonly associated with flashbacks, nightmares, and avoidance). Nobody qualified to make either of these diagnoses will mix them up accidentally.

For what it's worth, the person behind the website advertised by this diagram is not licenced to practice psychology in the state they currently call home. They also completed their doctorate in 2021 at the dodgy Christian fundamentalist anti-gay George Fox university

I wouldn't trust this person to look after my dog, let alone give diagnostic advice!