It's important to give the whistle-blower quite a few choices about how they can proceed.
First of all, they might not be fully aware of all the rules. You don't want them to lose protection just because they didn't read the rules carefully enough. Secondly, they're taking a huge risk with their careers. They need to be able to go where they think they may have a chance. In some cases, they will absolutely know that there are certain avenues that they cannot pursue. They need to have alternate avenues. They should not be forced, for example, to report to the very people who may be in charge of the wrongdoing. That would be a bad idea.