As I don't have a Mac to test this myself, I'm not sure why that's happening. However, if you follow the steps I'm posting below, this might help you with trying to run BFNS Remastered on MacOS.
(Credit to MichaelDoesGaming for the unmodified version of this tutorial)
1. First, right click on the BFNS Remastered application, then click “Show Package Contents”, and then click “MacOS”.
2. Once you have done that, open up another finder window (just right click on Finder and press “New Finder Window”) and then click Applications, and scroll down until you see “Utilities”. Then scroll down until you find “Terminal”.
3. Then open Terminal and type in: chmod (then press space) +x (then press space again) and then drag in the BFNS Remastered application. If you did it right, it should look something like this in the terminal:
chmod +x BFNS Remastered.app
Next, press the enter button on terminal. Now, go to your downloads and open up the BFNS Remastered application. Now open the application normally.
4. You will see an error screen saying that “filename” can’t be opened because it’s an unidentified developer. Just click the ok button and go to your system preferences, then go to security and privacy, Then you should see “filename” can’t be opened because it’s an unidentified developer. You will see a button saying “Open Anyway”, so just click it.
5. Then you will see an error sign. Just click Open. And there you have it, the mod should now be playable on your MacOS device. If this doesn't work, there might be another problem.
If doing the steps doesn't work, you'll have to wait until I get a Mac so I can test the mod on that platform myself and try to fix the issue. It could also be due to the MacOS version you are trying to play it on, but if the steps don't work, just tell me your MacOS version you are using because that could be affecting it.