The specification is intentionally open to sharing nodes, for example an instance may point to a method or Property node used for the type definition, or several instances just share some properties. This is allowed and intended behavior.

However, I do not see any reason why InstanceDeclarations should be shared between TypeDefintions.
I have not found any statement in the specification disallowing that TypeDefinitions share their InstanceDeclarations. I recently run into a CS RC accidentally doing this. This leads to problems in code generation and usage.

I recommend to add a statement to the specification, that disallows sharing InstanceDeclarations between TypeDefinitions. That shall not disallow references between TypeDefinitions like "GeneratesEvent".