We're dealing with life that doesn't follow any hard and fast rules. If you're expecting A+B to equal C every time, you need to rethink your expectations. I have a buddy that bad mouths seed companies because he got some bad phenos when buying single seeds. He thinks they should be carbon copies, doesn't understand genetic expression of different phenotypes within a lineage. Certain strains have more genetic disparity, so therefore, "strain dependent" is a valid answer, imo. Maybe "pheno dependent" is more accurate.