Default internal_users kibanaserver

Hello
this is followup to my other thread

after admin:admin user/pass is changed
removed all default users and added new users
is there a dependancy of any default users ? (kibanaserver)

if kibanaserver username is changed where else is this user pre-defined or is it in build
also if admin user is required or it can be removed

opensearch-node1 | [2022-06-17T20:54:40,849][WARN ][o.o.s.a.BackendRegistry ] [opensearch-node1] Authentication finally failed for kibanaserver from 172.19.0.1:48438
opensearch-dashboards | {“type”:“log”,“@timestamp”:“2022-06-17T20:54:40Z”,“tags”:[“error”,“opensearch”,“data”],“pid”:1,“message”:“[ResponseError]: Response Error”}
opensearch-node1 | [2022-06-17T20:54:43,349][WARN ][o.o.s.a.BackendRegistry ] [opensearch-node1] Authentication finally failed for kibanaserver from 172.19.0.1:48438

opensearch_dashboards.yml has default kibanaserver:kibanaserve user/pass