One of the more common topics covered is the idea that the whole thing is just a "phase" I'm going through. I get this one a lot also when I'm answering questions about being queer, although less in the sense that I just haven't found the "one", and more in the sense that I haven't found the "one set of genitals" that I'm actually attracted to. I do believe the two are slightly related, and both come from the mindset that I'm supposed to find a singularity and stick with it for the rest of my days.
The problem that I have with the "phase" mindset is it discounts any type of experience one's had before "settling," as it were. I've found it a lot in monogamous relationships as well where it's as though they don't or can't talk about previous sexual encounters before the two of them were together. Which is pretty silly, to me. Polyamory Weekly did a great podcast back in January about dealing with jealousy, and they made the analogy of how you need to practice dealing with jealousy just like you would practice getting better at the piano. Which is not to say that you practice dealing with jealousy by learning to play the piano - that the two are somehow tied together. It's the idea that just as somebody who is really good at the piano had to work to get that good, so people who deal with jealousy well had to work really hard to get to a point where jealousy doesn't destroy them anymore. I think the same hold true with sex. I mean, I'm sure there are those prodigy cases where the first time somebody has sex they are just fucking awesome at it.
But for the rest of us the first time is usually not all that smooth.
Sex takes practice to get good at, just like anything else. If you do really good practice regularly, then you'll get really good. But if you start out with the wrong way to do something, and then you only practice that wrong way, you don't get any better.
"Phases" of sexual identification is a weird way to put it. You can qualify it as a time period, and less of a conscious decision. It's like saying people who wait to have sex before they're married are just going through the "phase" of not having sex. Not that they've actively decided that they want to format their sexual relationships in a specific way regardless of whether or not they have a partner. It's the same regardless of the relationship format chosen. It's an active decision of a way to live a lifestyle, and maybe that decision will be reevaluated or even changed at some point in the future. It doesn't make one "phase" any less relevant than any other.