> I am curious though, would this job that mom goes back to actually be more "productive" than taking care of a four year-old and two-year old human child?

Actually, any job she likes? In this case, it's not for the baby, it's for her. Being with a child 24/7 has its toll, and people are social animals, they like being with others. In this case, work - especially white collar - is a kind of rest for parents. At least this is the attitude of many fresh mums (and dads) around me.

Taking care of a baby can be very social ... as long as the other mother's aren't all at work.

And what exactly are these jobs that are a rest compared to taking care of a baby? Are they actually economically productive or are they bureaucratic fake jobs?

I have noticed that many of my peer parents make parenting more stressful than it needs to be, and don't invest enough in learning techniques to make it less stressful. Like, some parents don't even invest in baby-proofing and then they are constantly chasing their toddler around. But, the first year of baby is always going to be stressful because everything is so new, just as the first year at a brand new job is always going to be more stressful than a job one is highly experienced at.