Reading between the lines, it looks like the story behind the story here is that this security researcher followed responsible disclosure policies and confirmed that the vulnerabilities were fixed before making this post, but never heard back anything from the company (and thus didn’t get paid, although that’s only a fair expectation if they’ve formally set expectations for paying out on stuff like this ahead of time…
I would argue that it is an ethical thing to do so if it sends a signal to pay whitehats appropriately.
Burger King is almost certainly going to experience no damage from this.
Their takeaway will likely be entirely non-existent. They’ll fix these bugs, they’ll probably implement zero changes to their internal practices, nor will they suddenly decide to spin up a bug bounty.