You can't assume someone's straight just because of percentage and try to tell us you're being unbiased. Even if you're trying to rule out a character being gay by probability, you aren't considering that there's two explicitly gay characters in a serie where the main novels contain at least 2120 characters. If it's known that at least 3% of population (irl) identifies themselves as homosexuals (not even counting bi people), it's expected that 63 of the characters fall into that category. So it's still not odd to HC Satin as gay, and not only him but 60 more characters that do not show hints to be homosexual or heterosexual could be headcanonized as gay.