According to Seedman/RSC, the Lebanese landrace is a great breeder and does not do as you suggest. Nor have many of my Mexican landraces. They have grown the same year in and year out and in different west coast locations. I am breeding an early sativa pheno line from the Lebanese. The best early one I got this year bloomed the 3rd week July and finished the second week in September, which is great for PNW weather. I had this gal cut and drying when the early rains came this year. I bred her to a Lebby sativa pheno male. They were from different sources; the female from BlueHemp/Swiss x the male from RSC/UK. Wide spectrum genes from the same landrace.
Off the top of my head from memory, Chem Dog/Dawg is a line from Dog Bud, grown in Colorado (Crested Butte). It is said to be a strain from either NorCal or Southern Oregon. I believe it is from NorCal, as it is similar to some other tightly held indicas that I have from some long time indoor growers there. I lived in Southern Oregon for years only a stoneâs throw from where some claim it is from there, but I never saw anything like it around there. Its origins may be extinct, but I do not think so. The original Chems from Dog Bud were few (11 or 13 seeds, I forget) and all S1 crosses. So they have hermie genes and they are a narrow spectrum of genetics from one clone of whatever Dog Bud was. All the Chems and OG Kush strains that I have grown were variable mutants. They grew stems from the center of leaves, they branched from leaf stems, they grew different under lights than in the sun. They also got really shiny fan leaves that turned variable odd colors in the fall, typically bronze. As for the differences in Chem lines, they vary slightly in genotype, and thus in expressed phenotype. The chemotypes are virtually identical, IMO.
One thing to note as well. Several groups are offering genetic profiling for strains to put into the public domain. Seemingly in fear that some big company will patent a strain, and prevent anyone else from growing it. However, note that in the US, only clones of one plant can be patented. You cannot patent seedlings or seeds from any plants (except in the case of GMO seeds). For non-GMOs, only one plant and its clones can get a patent. Every seedling of every strain of every kind of plant will have a different genetic footprint, so with the exception of clones and cuts, MJ plants cannot be patented in the way that many fear they can be. Some GMO patents are due to expire as well, so there will be non-patent GMOs out there soon. Plant patents are good for 20 years in the US.