A significant advantage of product-based planning is the ability to surface critical assumptions and constraints.
As a product you hope that it is there and will be fit for purpose but as you are not commissioned to deliver it, it falls outside your scope - and into your assumptions.
In this way, by defining the whole product set necessary for the project, and not just those that are in your scope, you can surface and document the critical assumptions.
This method is used in PRINCE2, the UK's government mandated method for the management of major projects A refrigerator is a final product with sub-products being door, shelves, heat exchange unit, fans, ice cube dispensers, lights, etc.
Each of the sub-products are made up of smaller products such as door handle, insulation, magnetic closure strip and internal covering.