Optional would imply the option exist in the torrent. Not requiring to go elsewhere and fiddle around. So it's nothing more than a lie, but no one really cares to call you out on Nyaa cause the encode is garbage enough to simply avoid. Tosho on the other hand generally cares more about tiny encodes so they're more apt to calling the lie out.

Just as a suggestion: if you don't want to mux the audio into the main MKV, perhaps consider just putting the files alongside it, in the same torrent.
This puts everything together, making it easier to find*, and you still get the optional aspect.

* Torrents get shared outside Nyaa, so relying on the description for linking two torrents together is less preferable than having a single torrent

Thats a lie man. Common. This isn't the first time a bunch of people got upset at you about this. Ive been here for over around a decade and you are the only uploader that tries to force someone to go to Nyaa iof they want the other audio. Everyone else that has a separate audio file includes them with the upload.
If you think its one person sorry to break it to you. I myself dont even bother with any your uploads at all anymore because of this crap. There is no reason you cant change but for some reason you wont. I hope they all continue to raise hell at you until you either change your methods or stop uploading. You cant  be so oblivious to understand that people would be upset when you deliberately exclude files. Likely the majority of people here dont torrent at all. A lot of Isp`s  block torrent sites like Nyaa. Hell mine sent criminal action notice warnings last time I used torrents so I stay away from them.  If you don want to add English audio just upload it as subbed only. Easy solution.

The key word is Nyaa, People on Nyaa are using torrents. The majority here dont so of course theyed be upset after downloading and expecting something to be in the file that isn't. My isp capped the bandwidth until 2021. I was stuck with their way overpriced cable tv because of that Once they removed the cap I cancelled cable tv.  A lot of people in rural areas have capped bandwidth for the month. When I had a cap I would get upset about corrupted uploads. Was a huge stress release once my cap was gone

If you are so pro Nyaa and so anti Tosho why are you even here at all. If you want to play games and cant take the criticism for it dont come to Tosho at all.

Trix you have issues. If you are getting so upset at the downloaders you feel the nee to insult them why bother uploading at all. The only thing you are accomplishing is driving more and more people away.