This is an interesting question and thanks for the link to @jon_duke’s nice slide deck.
Overall, I’d vote for a more holistic integration of the quality discussions. The subject of quality may be hard to break out to its own chapters, Quality and validation are threads that would naturally flow through many of specific discussions in existing chapters and these chapters are giving context for these discussions. For example, regarding data quality alone, there are at least 4 aspects of data quality impacting evidence quality (1) review vocab mappings, (2) checking source data quality, (3) ensuring ETL conventions are not violated, (4) evaluating fidelity and completeness of source data in the CDM form. Each of those are pertinent to existing chapters in the current book outline. For example, A discussion of how and why to evaluate the ETL conversion of a particular database discussion seems most natural in the ETL chapter etc. etc.
Similarly for clinical validation, there are aspects that are integral to a study design discussion, and cohort building discussion. A methods chapter would naturally discuss choosing an appropriate method for the scientific question, being clear about limitations and assumptions, checking assumptions, checking things like convergence and reproducibility etc.
That said, a summary chapter in each of the four overall areas that you listed that highlights general principles and tools for quality would be useful. The more general discussion could supplemented by specific discussions within detailed chapters i.e. ETL chapter discusses how to confirm that ETL conventions are followed and why the conventions are important etc.
In addition, in the intro, the Open science chapter could discuss benefits of community participation enabling constant iteration on quality across all the areas and generally describe the areas.