MySQL Enums have non-intuitive behaviour, why?

Question

This very helpful article explains some oddities about how MySQL Enums behave: http://melp.nl/2009/05/mysql-enums-and-booleans/

There is no discussiong about why that behaviour exists. Furthermore, in googling the subject I find only contradictory information and speculation, by 'bloggers' and other blind leading the blind.

Can someone please describe why MySQL Enums suffer from the behaviour outlined in the post. Here is one example of Enum oddities presented in the post, but there are many more:

mysql> insert into t values('1'),('0');
mysql> select b,b=1,b=0 from t;
+---+-----+-----+
| b | b=1 | b=0 |
+---+-----+-----+
| 1 |   0 |   0 |
| 0 |   1 |   0 |
+---+-----+-----+
2 rows in set (0.00 sec)