Different growing techniques (main lining/LST) can in no way alter the plants genetics, and to have two different expressions of the same type of strain, comes done purely to a slight variation in the individual plants genetic make up. Breeders who provide us with seeds to grow, have possibly 100s of mother plants that they fertilize to produce the seeds. Due to the random recombination of genes each and every time fertilization occurs, slight variations in the seed generation are a normal occurrence. This is known as "phenotypic variation" and although the seeds came from the same parents, slight differences happen due to slightly different chromosomes having either a more dominant effect or a recessive expression may arise due to the ever so slight differences within the genes of the pollen grains or female ovules. It is a bit like humans, even though we have the same parents, each child, even though they are getting half their genes from the same parents, will grow up completely different than their brothers or sisters. The reason humans are so different to each other, is that we have many more chromosome, which leads to many more types of recombination of our genes, leading to vastly different children even though they all have the same parents. Plants have far less chromosomes than humans, so breed reasonably identically, however due to very small differences in chromosomes between different parental plants, even though they are the same strain, will cause small differences in the next generation. This is what excites breeders so much, finding that one individual special plant that has something special about it, a discovery that could make it the next "super plant" with unique features. This is why seeds, even from the same packet, can grow quite differently from each other and from generation to generation too.
Hope this helps,........
Organoman.