Didn't read through all this, but the strains haven't "gotten magically stronger", there were Always Strong strains, Usually Indian Hemp/Indica which is what All these "stronger" strains are bred with. And even pure landrace Sativas were strong. But it's just because there so much new heirloom breeds out there that are All strong instead of Just average shitty grown Commercial bud. The same strain can be Two Completely different products in the end if one is Pure Organic harvested at Peak performance, and one that's Shitty Commerical Synthetic nutes and pesticides and harvested Much earlier.
Cultivation is an Art, and it's the Artist who have gotten Stronger and more Potent, Not the Bud that has Always been Just As Potent.