No I think there's confusion about lossless codecs. TrueHD/DTS-HD MA/FLAC are all lossless codecs. You can transcode between them infinite numbers of times, and the PCM they all decode to will be bit-identical. Just like zipping/raring a file. It's absolutely still transcoding not remuxing, the stream is decoded from one format and encoded into another. But there is no loss whatsoever. The wish is that Plex could transcode to FLAC (Dolby TrueHD/DTS-HD MA encoders aren't freely available) on the fly, or decode to 7.1 PCM on the server side to send to the client and be more universally compatible when things like CX TV's without DTS decode capability are in the mix.Yes there is no loss if you take it out of or change the container without manufacturing whole new streams from the original source in it (or if you take a long time manufacturing a new file rather than doing it on the fly). I think there might just be some confusion on terms we are using between us.
There is also hardware/gpu enabled transcoding which is faster but might be a little less precise (e.g. a little more artifacting occasionally in dark scenes with a lot of motion according to some reports). Plex's hardware transcoding was in some cases worse than software and they had hardware HDR transcoding, HDR tonemapping to SDR , etc. issues at first but they have been updating it.
I never said transcoding is not usable and probably not noticeable to the less discening eye but it's not 1:1 direct play, especially if you are using plex's default transcode speed.
"Direct Play" (pass-through) > direct stream (change/break the container type and pass the readable video/audio stream types already inside) > transcode (create new streams on the fly from the unplayable streams)