ktrace -c behavior

What behavior would you expect from this sequence of commands?

    ktrace -tw -p 1234
    ktrace -c -p 1234

Based on this...

     -c      Clear the trace points associated with the specified file
or processes.

...I would expect the second command to clear the trace point for
context switches.  It doesn't.  I have to specify -tw with the -c to get
that behavior.  This makes sense; it's just not what I was expecting.

Assuming we want to keep this behavior, can we clarify the -c flag in
man page?  I would suggest:

    If the -t flag is not specified, clear the default set of trace points.

Thanks,

Eric