Making sure we understand your actual question: is there some reason you object to attaching the federal return?

If not, just let Lacerte do its thing, and you should be fine.  On Screen 59, code 2, make sure you've only selected CA and not US.

On Screen 1, uncheck "federal" from e-file if needed.  It should prompt you to only e-file an amended CA return, and your client letter in forms should confirm that in what it tells the client is happening with that e-file.

On the explanation on Schedule X, you could add "no amendment to taxpayer's 1040 was needed." if you want to close the loop on it.

Let Lacerte figure out in the efile if it needs/wants to send the 1040 with it.  If it doesn't get sent, FTB has it from the original efile, so you shouldn't have problems.