What you are describing is the difference between
foundation breeds and
composite breeds. If you use that criteria for defining heritage breeds, quite a few more than the Delaware would have to be eliminated as heritage breeds.
I'm actually a real stickler for all animals referred to as heritage. Drives me crazy when I see people using the term purely for marketing. To me, heritage breeds have unique qualities (that have been lost in modern production breeds) , are historically significant and are healthy and hardy.
I like the ALBC definition (because it includes my Dels) but I also acknowledge that the SPPA has a different version. I raise only heritage breeds, not for marketing purposes, but because they are truly wonderful and special and deserve to be preserved.
BTW, it's not quite as easy to recreate the Delaware by crossing a BR and NH. Ask Kathy and all of us who now have her project Dels and are struggling to figure out how to get them true to the SOP.