A bit seasoned hacker will find out in no time that you are running flarum. This is a matter of minutes so the missing link will buy you just enough time to get a coffee before being hacked ;0)
No, but seriously, the system should be secure, right? Information cloaking will not help you much here. It could keep out the occasional script kiddie though, that's true. I do refuse to call those hackers.
I do agree on the license buying and then get it white labeled, very much agreed, but then you will have paid for the efforts. This goes for any company or person.
Bottom line, if you put down money it's white labeled, if you don't you pay with exposure. Reasonable enough?