It is technically impossible for them to post this thread in every section they need to, because then it would be posted in every player section. 
The “dozens of threads” the OP is referring to include these:
- How do I fix low volume output
- PLEX Low and High Volume Issue - Low Voice/Dialogue Audio Volume and High SFX/Music for Movies/TV Shows on Roku - PlayStation - Xbox - Smart TV Player
- Plex low volume - Samsung Smart TV, Samsung Soundbar, AAC stereo
- Let's finally solve the low audio issue please
- Consistently low volume from playback of videos
- Low Volume
- Volume too low on iPhone playback
Which, if you look at the threads, do mention iOS and Plex Media Player. But they also include complaints about low audio issues effecting the following clients:
- Android TV – which does not use MPV.
- Roku – which does not use MPV.
- XBox – which does not use MPV.
- Playstation – which does not use MPV.
- Samsung smart TVs – which do not use MPV.
- I’ll also personally throw in I’ve had this issue on LG webOS, which… does not use MPV.
I didn’t need to ask the poster if they posted in the wrong section, because I knew their tagging was correct based on the content of their post. They stated they had already researched this issue and mentioned all the other topics they had found on it (as I quoted above). All those topics which included other clients besides the Plex Windows Desktop PC app.
If I may be so bold, the person who needed to ask more questions here was you, since you were quick to blame MPV for the issues despite it only being a possible cause on one of the three players this topic was tagged with. You could have also done more research into all the previous topics the original poster mentioned. It only took me a couple minutes to collect that list for this post.
