If you look in event_ccase
CC7.x (even in 8.x), you will see that cleartool chact
itself does not generate a minor event.
However, changing the comment of any object does.
When you supply comments to a ClearCase command, your comment becomes part of an event record.
Some
cleartool
commands create a comment even if you do not provide one.
These generated comments describe the operation in general terms, such as “modify metadata” or “create directory element.”
User comments, if any, are appended to generated comments.
It is, as you have noted, a "minor" event, visible with cleartool lshistory -minor
.