I'm not sure whether it's expected behavior, filing just in case it's not.
http://kb.askmonty.org/en/alter-table/ says that changing a column name online should work; and it does for MyISAM, but not for InnoDB:
query 'ALTER ONLINE TABLE t1 CHANGE COLUMN i i2 INT' failed: 1915: Can't execute the given 'ALTER' command as online
Some other CHANGE COLUMN operations do work, even for InnoDB, e.g.
ALTER ONLINE TABLE t1 CHANGE COLUMN i i INT DEFAULT 1