current_schema not in sys.keywords

[yzchang]

While looking for available global variables, I noticed current_schema is not in sys.keywords (Oct2020 5e7ef9c3f0bd):

sql>select distinct * from sys.keywords where keyword ilike '%current%';
+-------------------+
| keyword           |
+===================+
| CURRENT           |
| CURRENT_DATE      |
| CURRENT_ROLE      |
| CURRENT_TIME      |
| CURRENT_TIMESTAMP |
| CURRENT_USER      |
+-------------------+

Why is current_schema not a reserved keyword? While it seems to behave like one:

sql>create table t (current_schema string);
#2021-03-30 14:44:16: client1: createExceptionInternal: !ERROR: ParseException:SQLparser:42000!syntax error, unexpected CURRENT_SCHEMA, expecting FOREIGN or PRIMARY or UNIQUE in: "create table t (current_schema"
syntax error, unexpected CURRENT_SCHEMA, expecting FOREIGN or PRIMARY or UNIQUE in: "create table t (current_schema"
sql>create table t ("current_schema" string);
operation successful