Thanks for this, I tried it out on my end with a cluster running DBR 12.2 LTS and I was able to get it to work.

CREATE TABLE test (id int, time timestamp);
ALTER TABLE test
SET TBLPROPERTIES('delta.minReaderVersion' = '1', 'delta.minWriterVersion'='7');
ALTER TABLE test SET TBLPROPERTIES('delta.feature.allowColumnDefaults' = 'enabled');
ALTER TABLE test ALTER COLUMN time SET DEFAULT CURRENT_TIMESTAMP()