In MySQL, historically GROUP BY was used to provide sorting as well. If a query specified GROUP BY, the result was sorted as if ORDER BY was present in the query.
mysql-5.7> CREATE TABLE t (id INTEGER,  cnt INTEGER);
Query OK, 0 rows affected (0.03 sec)

mysql-5.7> INSERT INTO t VALUES (4,1),(3,2),(1,4),(2,2),(1,1),(1,5),(2,6),(2,1),(1,3),(3,4),(4,5),(3,6);
Query OK, 12 rows affected (0.02 sec)
Records: 12  Duplicates: 0