RMAN Incremental Backups?

"If no level 0 backup is available, then the behavior depends upon the compatibility mode setting. If compatibility is >=10.0.0, RMAN copies all blocks changed since the file was created, and stores the results as a level 1 backup. In other words, the SCN at the time the incremental backup is taken is the file creation SCN. If compatibility <10.0.0, RMAN generates a level 0 backup of the file contents at the time of the backup, to be consistent with the behavior in previous releases."

So yes, that's it. Even in the Oracle 11g OCP course and exam, the information given is for Oracle 9 (pre 10g). Seems like a major functional regression.
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Original problem.

Am I not understanding something about rman????
Using oracle 10g standard edition and rman.

No existing backups.

When I run repeated level 1 cumulative incrementals, the appear to back up everything (like a level 0 would).
My understanding is that if a level 1 is run w/o an existing level 0 backup, it will generate a level 0 backup.
All subsequent level 1 backups should be level 1's as expected.

If I explicitly generate an level 0, followed by level 1's it all works as expected.

I am determining what got backed up by the size of the resulting save sets.

Do I have to do an explicit level 0 and then explicit level 1's? I thought not.