Should a product marketing team have a growth product marketer? If so, when, and what should we think about their focus and scope of work?

If there’s a Growth Product & Engineering team that has enough work to support a growth product marketer, then I’d say it makes sense. Their work and scope should be closely mapped to the roadmap of the Growth Product team. Typically will be focused on experiments to improve core user metrics through product adoption, rather than big GTMs / product launches. 

Product Marketing teams need Growth Product Marketing Managers. This close relationship is especially important when the initial product launch and go-to-market moment is done and the focus shifts to growing usage of and engagement with the product.

Product Marketing Managers often refocus on the next feature/product launch, instead of having the time to prioritize growth work. The Product Marketing Manager is responsible for understanding product-market fit and building messaging and positioning, while the Growth Product Marketer takes that messaging and implements various tactics to drive growth through feature adoption, activation and retention.

I believe all product marketers today would strongly benefit from having a growth mindset and skillset -- but whether or not that's the entire charter of their role depends on the core goals of their specific product area and your business priorities.

For example, you may have products that are highly effective for landing/driving revenue, while you may have others that drive retention or lead to more upsell pathways. The latter is a great place to have a Growth PMM, either as a dedicated head or with adoption as a significant part of their specific KPIs.

As another example, you may have a platform with a free trial/paid conversion strategy (e.g. potentially traditional PLG for some/all segments). In this case, it may make sense to have dedicated PMM(s) that partner with PM and demand gen to identify and build out use cases in product, supplementary external assets (testimonials, guides, video examples, etc.), and even explore specific pricing/packaging/offer options aligned to optimize those paid conversions.