Unrelated Greek word? Platonic here refers to the nature of Arthur and Lancelot’s relationship. It’s a platonic relationship, rather than romantic or sexual one.

I think you’re somewhat understanding what Platonic love is. In modern usage, I’d say that Platonic love is a really strong form of love, stronger than could be called friendship, but which lacks a sexual or romantic dimension (or at least lacks enough of those to characterise as a romantic or sexual relationship).

But it might also be interesting to look at what Platonic love meant to Plato. I’m not an expert. Not even close. But my understanding is that he might have meant it to be the most perfect form of love. We have the phrase “platonic ideal” that we use in other contexts to refer to something that is the most perfect version of that thing, and I think Platonic love likely originally meant that, for love. It was love of the body, the mind, and the soul. Not less than romantic love. Not equal-but-different like the modern usage of the term. But instead encompassing everything that romantic love is and more.

But I’ve only read extremely shallowly into this matter, and would love to hear more from someone who really knows their stuff.