Wow, that sent me down a rabbit hole of searching. I am old enough to have messed around with lots of VHS tapes in my day, but I was still too young to know what was going wrong with the picture. Reading how Macrovision screwed up the picture through desyncing the scanning explains why some of the “non-authentic” tapes I got never played right for me.
Really interesting perspective on this issue. Out of curiosity at one point, I got my hands on the porygon episode and the flashing is certainly jarring. It didn’t really bother me, but my wife said it gave her a headache (just a minor one, not a migraine fortunately). I had no idea that there was so much that came out of that incident. Really neat!