mostly true, in eusocial organisms there is some evolution also driven by kin theory. Though not as powerful as direct offspring aiding genetically similar helps continue the genetic line hence gay uncle theory. Their is a weak non-zero r^2 correlation between genetics and homosexuality. It would be an awful answer to explain homosexuality as genetic but it is not completely explained away by your evolutionary model. Gay people also still reproduce especially women. If it was a completely detritous evolutionary effect it wouldn't;t occur in nature. Ultimately it isn't a yes or no thing unless we define a more specific definition of natural.