Any work is never going to be completely free of personal interpretations. And personally, I also think that the authorial intent, while not the only valid thing, IS important; especially in cases executed too ambiguously like Riddick.
Riddick was supposed to have scene which showed that the lesbian character is not lesbian. It has been cut out. So no, I have no problem with screenwriter, but with person who decided to cut it out, because in the end it made the movie send damaging, dangerous message which puts lesbians in danger, as the myth it encouraged fuels sexual harrassment and corrective rapes.
If people are prejudiced, then they can still find ways to have prejudices confirmed in something even despite the best efforts of an author.
They don't need to look out hard for the way, since we talk about overrepresentation of storylines with lesbians ending up with/falling for/sleeping with men (and enjoying it), which is apparently pushed by people as bigoted as the audience it's intended to pander too.
Visibility matters. It changes people's views. The majority in US now supports same-sex marriage while decade ago it was significantly lesser number. It didn't just happen by itself, but due to exposition to positive representation of queer characters in the media (who as GLAAD reports show, are in majority gay men).
I mean if there was a hypothetical story about someone who clearly identified as gay (or straight) coming to terms with being bisexual, then people could still see homophobic views about gay and lesbian people just needing for find the right person confirmed, even though that's a real type of thing that does happen to real people.
In the context that majority of lesbian storylines introduce lesbian sleeping with a man (and liking it) trope, and that mainstream movie with famous actor about lesbian being turned by the right man is made and no one except for lesbians finds any problem in it, yes, that storyline would be problematic.
Few months ago I was writing to BBC with complaints about two of their shows introducing aforementioned trope. In one, the lesbian character was basically sexually harrassed by the guy who wanted to turn her, and suddenly (after he showed his "softer" side), she fell in lust with him. In another, lesbian told man who was hitting on her that it will never happen because she's lesbian, and month later she ended up in lustful sex with guy.
Each time they wrote me back that they are just reflecting the reality and there are lesbians like those characters.
I've read that right now another BBC show introduces such storyline, this time about lesbian falling for her sperm donor.