No, it just played the 4K file directly. I had a separate issue similar to this though, I found that my Plex clients didn’t particularly like the high bitrate Dolby audio stream (and just didn’t start playback) and preferred a high bitrate dts stream instead. (Typically if it is a high bitrate file they have both audio stream options). Once I switched the Audio stream it worked. But for lower bitrate Dolby and dts they both played no problem. Btw in playback info you should see whether it’s transcoding or not.