Hello, Niniann.
It is indeed a false positive. rcedit (the tool that does the changes to the bootstrap and game's executable to apply the new icon and Metadata) seems to trigger these. It was supposed to be fixed since R5. 11u3, but if it still happens, it's possible that another issue causes it.
I'm looking into a permanent fix for it, alongside pushing a stop gap fix (rcedit not updating the bootstrap's Metadata) so Windows Defender doesn't delete it all of a sudden. Although, it seems to be a bit rare.
EDIT: When I say rare, it's a bit of a luck of the draw. Occasionally, it would false flag it. But most of the time, it doesn't. Not sure why. But I am looking to that fix. A potential workaround is to simply build again.