The JPO has announced that it is expected that the attachment of a certificate of registered matters (except those issued by overseas authorities) to procedural documents will no longer be required as of April 1, 2022.
Measures taken in response to the "Act to Partially Amend the Act on the Use of Information and Communications Technology in Administrative Procedures, etc. for the Purpose of Improving Convenience for Relevant Persons and Simplifying and Increasing Efficiency of Administrative Management through the Use of Information and Communications Technology" which went into effect on December 16, 2019.
Japan Patent Office
https://www.jpo.go.jp/system/process/shutugan/madoguchi/info/tohki-syoryaku.html