cannot alter update option in TDengine database?

I know that there are 3 update options in TDengine database:

• 0: data cannot be updated
• 1: update entire row
• 2：update some column

If I create a database with update option equals to 1, why I cannot alter this option to 2

taos> create database db update 1;
Query OK, 0 of 0 row(s) in database (0.007480s)

taos> alter database db update 2;
DB error: Invalid database options (0.000722s)

The update option is special, it is not allowed to be updated once the database is created.