Again, this is a semantic debate. The real question is how is this distinction meaningful or useful? Lately, semantic debates have been a huge political strategy, so that's where my mind goes: What is the endgame of this argument?

(If this really is just a semantic game with no serious implications, a la "is tomato a fruit or a vegetable?" then let me know)

Like regardless of whether or not white is "a color" or "lack of any color", it still functions like a color for most practical purposes. Yeah, there are some exceptions (you need to bleach something to get it white, rather than dying it) but there's plenty of overlap too. White is a color of paint you can buy, it's a color in the hexadecimal color system, etc.

But I'm not particularly attached to specific term "sexual orientation," though, and if you have a different term you'd prefer to call that category, I'd be curious to hear it.