It would really depend on context. It's not like I'm offering them parenting advice or bringing up the topic of having children, so this would be something unprompted from them.

I don't have kids and I'm never going to have kids, so they're are probably some things about having my own children that I wouldn't understand. However, I was a heavily parentified child with a large extended family who was in charge of child care by age 10, alone, caring for multiple children ages 1-9 every day for years before and after school and through the summers including all house chores, cooking, cleaning, and all aspects of keeping the children - so often they are unknowingly very, very wrong in their assumptions about my practical experiences in caring for children. They are right that I'll never know what is like when the children are my own but wrong to think I don't understand the daily grind of childcare. Since I don't talk about that part of my life to many people, though, I wouldn't expect them to know that.

Sometimes using that phrase means the parents are using their children as an excuse to avoid their own responsibilities or are existing their own poor behavior towards their children. In those contexts, I absolutely judge the adult for using children to excuse their own lack of personal responsibility.