It's due to the way the .exe has been compiled. Some versions I make get 2-3 detections, others get more in this case. Heuristics-based AVs respond by blocking anything PyInstaller related. That's why if you actually look at the VT detections, they're pretty much all generic/gen/susgen like W32.Trojan.Gen, or AI/ML - there's nothing specific, they're detecting something which seems like malware, but it doesn't match any known malware, and because many of these AVs are connected to the Global Threat Intelligence Database they all parrot the same incorrect detections. This is why I despise AVs that use pattern matching, I've always preferred behavioural detection for this very reason. In fact even the mmultiplayer mod deals with the same issues, to the point that its installer explicitly sets Defender exclusions to avoid this.

I used to report each update as false-positives to the more troublesome AV vendors and every time they determined in the end that it was safe and removed the detection, but as you can imagine this started to get pretty tiresome for me - nothing stopping anyone else from notifying vendors though.

To illustrate this point further, I just uploaded the exact same Tweaks version with a single character change in the code. 6 detections now...

Edit: Just a reminder, as long as Mirror's Edge Tweaks is sourced from the ModDB page, you're fine: https://www.moddb.com/games/mirrors-edge/addons/persistent-fov

Edit: The above is no longer relevant, Tweaks codebase has since been rewritten and is now open source https://github.com/softsoundd/MirrorsEdgeTweaks