Interestingly, this does yield a jobid that I can use, even though it is not THE job id. e.g. using that query I get

72A6BEB9941ED146AD41CCEED345E01D

the actual job id (from sysjobs) is

B9BEA672-1E94-46D1-AD41-CCEED345E01D

Comparing the two, you can see that the last eight bytes match. I'm guessing that SQL Agent overwrites the first eight bytes with something of its own.