Hello Kingofrhye,
regarding your arguments:
The nucleus develops up to late puberty. I cite from the ebook "According to Hofman and Swaab the “thrusting center” at birth has only 20% of the cells found at 2- to 4-year-olds. It achieves its full development in males and females around the age of three. After that age, it gradually becomes smaller through the years in females. The authors state that: “This postnatal period of hypothalamic differentiation indicates that, in addition to genetic factors, a multitude of environmental and psychosocial factors may have profound influence on the sexual differentiation of the brain.” Ahmed et al. (2013) challenge the view that this structure does not change during puberty in males. They have shown that it is enlarged with new cells during puberty in male rats and that in male rats castrated before puberty it gets smaller. Schulz et al. (2009) propose that all the postnatal period up to late adolescence is a second window of opportunity for the sexual differentiation of the brain structures, including the “thrusting center”, implicated in homosexuality." In adult castrates the nucleus gets smaller.
-The nucleus can be of normal size and still not functioning properly (this is what happens I think in persons who masturbate excessively due to stress or addiction). Or it can be small and not function due to being small. Or it can have other problems not detectable with present knowledge.
-As for the causation or correlation: if removing modern diet and stress changes sexual orientation in the heterosexual direction, this would show causation. Intentional or unintentional treatments using stress management or diet (religious lifestyle, therapies advocating drug abstinence, raw food diet, conversion therapies)report change in sexual partner preference. The conversion therapies in use today report low success rates because they address few of the stress sources. Even the best therapy cannot wholly change the modern environment (the artificial light, noise, chemical pollution, the low nutrient soil and foods etc.). The causation can be showed in a trial. I think homosexuality develops during months-years of stress, so such a trial would need to be at least some months long.
-I doubt that those homosexuals who do not like to be bottoms, are tops as often as and similarly to heterosexuals. They are probably bisexuals or situational homosexuals, with a lesser affected nucleus. I do not know of any study on this, but in general, the cultural perception since ancient Greece has been that the bottoms are the long life homosexuals, while the tops are situational homosexuals.
-The theory explains female homosexuality as well, because females have equivalent muscle movements in the vagina and the equivalent urge to "engulf". In animal tests the females with lesioned nucleus do not accept intromissions.