I do also select ContentControls (CC) from the template pages before copying to the document. It works.
I have actually edited the template while working with the document by refering to thisDocument (!?).
I do this when the template changes. There are complex elements contained within CCs. When I update some of these I also want to update these in the documents based on the template. I could create Building Blocks (BBs) out of the CCs, but that's few more operations every time a change is made, to update the BBs. Also, I want to replace old CCs in the document with new from the template having the same title, without looking up the correct BB for that CC.