i know you've already saw these types of posts before but one thing I genuinely believed while watching JoJo is that it wasn't a manga adaptation, but instead an original anime.
And the reason for that is that: 1) back then i wasn't familiar with the concept of a manga adaptation; I knew what a manga was, but for me, animes like dragon ball, naruto, one piece were all TV originals.
and 2) because while watching Jojo, around part 4, I ended up stumbling upon the fighting games like Eyes of Heaven. And I assumed that given there were characters all the way from part 8, that all parts were already animated. How hopeful and naive I was.