This is an excellent point. My reading about attachment and detachment in our lives goes like this.
Being with someone or spending so much time with someone or even something doesn't mean that person is attached or detached. It totally depends of how much you posses that person or thing in your life, how much you add the word 'mine' to that.
If it is your, you want that person or think to behave or work according to your expectations. That's why parents break down when their child is going in a different path than they expected, and even we feel upset when our favorite car breaks down.
What you have to understand is nothing in this world is yours. You are borrowing it, even your body. You can't even control when your body get sick.
When you start to understand this, that's where you detach. You can do all of your responsibility for your children, guide them and still detach from them just by expecting them to behave according to what we expect. Their life is not ours to control. You can eat healthy, go to gym every day, treat your body the best way possible - still accept, this body is not yours, it still can get a cancer, or become ill tomorrow. This is what detachment means for me.
I will link an article I wrote about Buddha's teachings about attachment and detachment. Hope this will add a value to your perspective, And thank you very much for sharing such a wonderful piece of article.
The Buddha Explained His Teachings To A Young Man — But In Simpler Words