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We have a use case where it would be helpful to be able to filter a View of nodes by node type, only including node types that have product reference fields. This may be possible as a simple extension of the product node type filter that instead of showing checkboxes for each node type just displays which product types it will filter for and doesn't let the user change. It might be nice to have a negation checkbox, though, so you can choose if the View could also display non-product referencing node types.