I just tried to flag a post, and the only option I had was "Other".
I can see the full set of options when flagging other posts (and I refreshed the page to check it hadn't loaded incorrectly), so it's unlikely to be something local to my computer. I have 31 helpful - 2 declined flags, so I also doubt it any sort of automatic block from flagging for whatever reason.
I can't find anything that mentions it and I don't know of any reason you would be allowed to flag, but not use the default options.
Was there something I did that caused this? Or was it just a fluke/random bug of some form? Or even a feature I don't know about?