As the white is recessive, breeding back to normal CL will produce autosexing chicks that look like regular Cream Legbars, of course since recessives don't show up unless homozygous.
My understanding of a 'new variety' is that it would breed true for 5-years....and that would mean parents and offspring looking alike and not alternating normal and white- as I understand it. As yet, I have only heard of one person getting white to the F2 (two white parents) - and the autosexing was a bit unknown as I recall from a photo of the chick and discussion -- and no adult follow up was posted that I know about. Perhaps this is some of the source of confusion where people say that they will be 'breeding true' for multiple generations if in their eyes that incorporates normal CLs to put autosexing in every-other-generation.
Interesting topic, as enola says and food for thought. To me it would have to be 5-years of breeding white-to-white producing autosexing chicks and not breeding back to normal to be considered breeding true as I understand the APA requirements.
And i too have only ever just once heard of a white to white parent producing a single white chick. Other than that i have never heard of 2nd gen white CL from 2white parents.