ISO 23387 etc proposes a method for managing property libraries and organising them into templates. The (new) bsDD meets these requirements and is the only free resource that i am aware of. My impression is that manufacturers in particular are keen to take control of these resources away from open standards, and this may be happening behind commercial pay-walls.
ISO 23387 contains an EXPRESS definition of how a ConstructionObject can/should be mapped. I think there should be at least one example that follows this definition. The people who wrote the standard should at least prove the feasibility/applicability in an example. A file in IFC (aka STEP), XML or JSON format.
There should be a DataTemplate and a matching DataSheet for a concrete product.
BTW I don’t get the impression that manufacturers want to hide data behind a PayWall. I see the need for basic properties of products to be published and freely accessible. e.g. product data is largely freely accessible as a PDF. ISO 23387 makes it possible to process this data through automated processes.