"...the destination volume is then expanded to reach the extent
of the partition (so if you cloned a 1TB drive to a 2TB drive, the
destination volume would be 2TB when you're finished)."
"The source and destination must both be actual volumes (i.e.
not a subfolder on a volume)."
So I just did a block level copy of the entire partition
(volume) that timemachine was on, copied the non-timemcahine stuff
to the other new partition, then deleted it off the new timemachine
partition. Result: New drive has timemachine on its own partition,
user data on the other partition.
NOTE: if you are copying timemachine data using a different
computer than the one which will be using that data, I recommend
turning off TimeMachine before starting the clone, lest when the
copying is finished and the TimeMachine volume mounts again, the
TimeMachine backup files are updated with the state of the computer
you are using.