ACL permission works on insert and update operations. If during the update operation, ACL list is encountered on server side, it updates the ACL permission too at the same time. If you have same ACL permission as the time of insert, this is not going to impact your doc.
Also, if you want to have global ACL permission for all your data, you can just call App42API.SetDefaultACL(aclList) on startup of the app. In this case you dont have to pass the ACL list in service reference. If you do so, service reference ACL will be used to set the permission overriding the value of global ACL.
Let me know if it helps.