In a play based environment there is "learning" and "educational concepts" involved in all the activities that would be available in a developmentally appropriate classroom. I believe strongly in the value of a play-based experience for all young children. We are a lab school and a big part of what our teachers do is to promote the value of play to our college students (pre-teachers). The students are taught to look for the underlying value of the play that they see. Harvard Graduate School of Education has great information about one of their projects called Making Learning Visible. I think if you look at what you call non transparent academics, the challenge for us as teachers is to make the learning that is occurring in our classrooms visible to others. There are many ways to accomplish this and we need to find what works for us in our own classroom setting.
Another piece of the puzzle about focusing on "academics" is the role that social emotional development plays in the readiness of a child to enter kindergarten. Children are experiencing through play the skills needed to support their development.
"Research shows the link between social and emotional skills and school success is so strong, it is a greater predictor of childrens' academic performance in the first grade than their familial background and their cognitive ability." This article I have linked talks about the role of play and social emotional development.
I'm not sure what the original question that was posted in this series was directed towards, but I do know that we as professionals need to be vocal in our support of doing what is best for young children.