Through testing, we were able to determine that the problem was in the default value of the forward_origins parameter of the SELECT pglogical.create_subscription(...) procedure.

The documentation at https://github.com/2ndQuadrant/pglogical specifies that the forward_origins parameter identifies an "array of origin names to forward" and, by default, value is'{all}'.

In our tests, we set it to a null array '{}' and the replication works. Therefore, the correct subscription (in any direction) is:

SELECT pglogical.create_subscription(
    subscription_name := 'sub_node1_to_node2',
    provider_dsn := 'host=127.0.0.1 port=5432 dbname=dbtest02 user=postgres password=MyPAssword',
    replication_sets := ARRAY['replication_set_a2'],
    synchronize_structure := false,
    synchronize_data := false, 
    forward_origins := '{}' 
);