The docs state that creating tables is not supported, but I am unsure about the '[TEMPORARY]' part. In practice, it is not verboten, see below for 5.6:

  mysql> SHOW VARIABLES LIKE '%gtid%';
  +---------------------------------+-----------+
  | Variable_name                   | Value     |
  +---------------------------------+-----------+
  | binlog_gtid_simple_recovery     | OFF       |
  | enforce_gtid_consistency        | ON        |
  | gtid_deployment_step            | OFF       |
  | gtid_executed                   |           |
  | gtid_mode                       | ON        |
  | gtid_next                       | AUTOMATIC |
  | gtid_owned                      |           |
  | gtid_purged                     |           |
  | simplified_binlog_gtid_recovery | OFF       |
  +---------------------------------+-----------+
  9 rows in set (0.00 sec)
  
  mysql> CREATE TABLE test AS SELECT 1;
  ERROR 1786 (HY000): CREATE TABLE ... SELECT is forbidden 
  when @@GLOBAL.ENFORCE_GTID_CONSISTENCY = 1.
  
  mysql> CREATE TEMPORARY TABLE test AS SELECT 1;
  Query OK, 1 row affected (0.03 sec)
  Records: 1  Duplicates: 0  Warnings: 0

So perhaps it is still 'not supported', as in our experience it does indeed cause some issues, probably avoidable if you are willing to do dirty reads (READ COMMITTED).

I wonder if REPEATABLE READ is a good default anyway.