@eskimo, hello!
I just faced the same issue while updating my macOS game.
My entitlements are:
<key>com.apple.security.app-sandbox</key>
<true/>
<key>com.apple.security.network.client</key>
<true/>
But when I try to upload a build to AppStoreConnect, I see com.apple.developer.game-center entitlement added.
The issue only affect version with in-app purchase enabled. The version without in-app purchase is not affected.
Any news or ideas about how the case can be resolved?