The description of the TrustList in https://reference.opcfoundation.org/GDS/v105/docs/7.8.2.1 tells: "The TrustList file is a UA Binary encoded stream containing an instance of TrustListDataType (see 7.8.2.8)."
Add a clearification, that this value is not encoded as an extension objec, but as a plain structure.

E.g: "The TrustList file is a UA Binary encoded stream containing an instance of TrustListDataType (see 7.8.2.8). The encoded structure is not wrapped in ExtensionObject."