Yup, this looks like it was introduced by this commit:
IMPALA-4616: Add missing Kudu column options
Adds support for missing Kudu column options in ALTER TABLE
(it was there in CREATE TABLE already):
Also adds support for adding nullable columns with default
All of the above was not originally implemented due to
limitations in the Kudu client, but have since been fixed:
Testing: Updates and adds relevant test cases.
Reviewed-by: Marcel Kornacker <email@example.com>
Tested-by: Impala Public Jenkins
Should be easy to fix, thanks for filing!