I don’t see why there needs to be a distinction between pedagogical content knowledge and TPCK? The knowledge part of PCK is not a simple concrete factual knowledge of textbook-like information. This knowledge includes knowing what teaching approaches fit the content, and likewise, knowing how elements of the content can be arranged for better teaching. This should include incorporating new technologies and applying them to learning.
PCK stands on a careful balance of content and pedagogy. It certainly shouldn’t be a simple consideration of both content and pedagogy used together but standing in isolation. The balance is rather an amalgamation of content and pedagogy thus enabling transformation of factual content into relevant teachable forms. PCK represents the blending of content and pedagogy into an understanding of how particular aspects of subject matter are organized, adapted, and represented for instruction. Different subject areas in particular STEM education might put a higher emphasis on content than for example teaching children how to read which would have more emphasis on pedagogy. Regardless of the area pedagogy and content need to join together to create something that students can experience and grow from.
Keith