which still showed a 7.7% concordance rate for male homosexuality
In isolation, this number tells us nothing. What is important is the gap between concordance rates for MZ, DZ, and siblings. There are several popular hypotheses that predict a large effect of prenatal environment. In fact, the particular paper give 7.7% MZ, 4.2% DZ, and 4.5% siblings, so it detects no effect of prenatal environment and does suggest genetics.
In isolation, this number tells us nothing. What is important is the gap between concordance rates for MZ, DZ, and siblings. There are several popular hypotheses that predict a large effect of prenatal environment. In fact, the particular paper give 7.7% MZ, 4.2% DZ, and 4.5% siblings, so it detects no effect of prenatal environment and does suggest genetics.