Is this correct?
No, it is inappropriate. According to psychologist and art therapist Yana GRYSHEL, outsiders should not make comments to other people's children. However, it is acceptable to politely ask a child about something, for example: “Don’t throw the ball so hard” or “Please be careful with the castle you built.”
It is a different matter if there are no parents around and the child's behavior may threaten their life or health — in such cases, intervention is necessary.
If your child is reprimanded in your presence, the expert recommends responding calmly: “Thank you for your opinion, but raising a child is the responsibility of the parents and mine!”.
