Sorry if I'm reviving something totally dead (oyz), but this is a really interesting question.
Recently I discovered a deep love for Ruko's voices, so I went to long-sleeper to check out their different voicebanks, which is when I learned the "9:1" thing. I do think it's kinda weird that nobody ever seems to talk about it. As for gender pronouns, the reason why Ruko (or rather Ruko's creators) never mentions pronouns is quite simple: all the information comes from Japanese, which rarely, if ever, uses third person pronouns -- it's just part of the structure of the language. As for gender, it actually does get a mention: Ruko is referred to as "futanari", which literally means 'two kinds', and most commonly translates to "hermaphrodite" -- which is a bit outdated in the English language, so perhaps "intersex" or "bigender" is more accurate. I think this kinda gets ignored sometimes, possibly because people don't know or because Ruko looks quite feminine (figure-wise, at least), so many default to "she".
I personally refer to Ruko as "they" (singular) when referring to the character, "she" when referring to the female voicebank and "he" when referring to the male voicebank, for the sake of clarity. So to answer your question, I don't think it's that weird at all, and think you should use whatever you think works best, since for Ruko, it's kind of a big gray area. Apologies for rambling, and I hope this helps ^.^