I think the answer is a bit more complicated than yes/no. The way I see rpf is that we create stories with "characters" based on the idols (or better yet, their public persona). So we do have some material to base our characters on, especially since so much of their lives are made public, and video content, interviews, etc. can help you with understanding them better. But what they show will always be a very polished and curated image that will never be able to fully reflect who they are as people and off camera. And each fan will have a different read on them based on what content they've seen, which interviews they've read and even just how their personal experience influences their interpretation of the idol's actions.

So imo there are some things that feel disconnected from the perception I have about certain idols, but it's my interpretation of them and not necessarily the correct one. And regarding fics and writing, I find that even things that feel "out of character" can be enjoyable if the writer can find a way to make them believable and work it into the narrative.