redolog groups,threads

I have rac database with 2 nodes, 19c with 2 nodes database 19.3 on linux 7

SQL> select inst_id,group#,thread#,members from gv$log;

INST_ID GROUP# THREAD# MEMBERS

---------- ---------- ---------- ----------

1 5 1 2

1 6 2 2

1 7 2 2

1 8 1 2

2 5 1 2

2 6 2 2

2 7 2 2

2 8 1 2

the above shows that each instance have 4 redo log groups each with 2 members.

my questions are:

1- when i issue on node 1 (alter database add logfile group 9 thread 1(+DATA,+FRA) size 100M) it create the same group 9 on both nodes knowing that the command is issues from only node 1

2- when trying to drop and inactive group 6 from a node, an error arise , cannot be dropped as each instance must have at least 2 groups knowing that it has 4 groups as shows above