PQR: a common Misunderstanding when it comes to Starting Materials

In Chapter 1.10 of the EU-GMP Guidelines the requirements for the Product Quality Review are described, also demanding a "review of starting materials including packaging materials used in the product, especially those from new sources and in particular the review of supply chain traceability of active substances" (1.10 i)

But what does this exactly mean? Does a manufacturer only have to re-state who manufactures the API because always the same company is and was used? "No" is the answer according to a blog published by the U.K. Medicines and Healthcare Products Regulatory Agency MHRA. Ewan Norton, a GMDP inspector of MHRA's inspectorate, criticises that chapter 1.10i is often "misinterpreted by companies as simply being a requirement to state the manufacturer and supplier of the API, but actually the requirement is to fully map all the parties involved in the supply chain and periodically re-assess this for accuracy.  Chapter 5 (5.29) provides more detail on this and makes it clear that the Active Substance supply chain traceability starts at the 'active substance starting materials' i.e. the Registered Starting Materials for the API manufacturing process.