Were you able to look into the book that got cited? The screenshot about falling in love with Bai-Niang says that it was when Miyazaki was in high school, so we can ignore that one. The documentary quote sounds in the same vein as that to me: that in high school he had girlfriends of that age. There could have still been a problematic age gap there, though, but who knows.

My biggest question was what kind of love we are talking about here, to me it sounded more like platonic or one-sided romantic love rather than outright sexual, but it is just vibes talking here.

Sidenote: I find it weird how much weight is given to the verb "love" sometimes: it gets used very loosely when you say you love spaghetti or your family, but suddenly when you say it to a close friend everyone makes a big deal out of it. My aroace ahh is showing here lol