no plex has never enabled transcoding TO x265.
when you look at the dashboard, the first line is the from, and the 2nd is the to.
Now, you might see plex REMUX or DIRECT STREAM x265/hevc, which is not transcode, it means switching containers, like from mkv to mp4, or whatever the client needs.
direct stream is much less work than transcoding, however it still requires a lot of processing and IO, and some servers simply are not capable of it.
more likely what is also happening is the AUDIO is being transcoded, and processing truehd is not trivial either.
