LABELs and COMMENTS are not considered objects. They are attributes of objects. So they are not handled in the same way as objects such as indexes or tables. The only way to stop attributes from being compared is using the ruleset.
With the two column rules set to N, we tell RC/Migrator not to compare column labels or column comments, which means we keep the target values.
The need for setting these rules to 'N' can be avoided by ensuring that the input file includes the complete DDL of the objects that you want to compare.