Edit: Added v6.0.2.5
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It is possible to make it centered. But it won't be automatic. Some people don't want it centered after zooming or moving. I think it might be possible to add a button or shortcut to do this. I'm busy right now, might add it in next month's update.

Yes, it is AI-Based Recognition. I use a pose-related model and estimate the pose from the frame. Once I know what the pose is, I rotate the video.

I can set the default when entering the watch page/fullscreen and zoom in/out according to the desired value. But I think that's what you really want. To make the subtitles appear, try using my extension called "Youtube Subtitle Position" first. It can move the subtitle position and has an option to remember that value. If it really doesn't work, send request via "issue/suggest" button on the options page and attach a link to the screenshot of the missing subtitle. I think it's strange that the subtitles are missing.

Thanks. There will be no subscription in this extension anymore and forever. I will think about creating something else instead.

Edit 2025-02-06
Ok, I will increase the hitbox size in the next update. Please update the extension again in a day or two.
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Permission is not related to subscription. This permission is required for adding buttons to YouTube tabs. Previously it was used in manifest v2 too, but in v3 the user has to enable it manually. In all Chorme extensions that add anything to a page it has to have this permission but in chrome It enable automatic, unlike Firefox.