Clarification from Apple on Internal vs External users apps for testing

I have seen numerous reports off the web about folks using AdHoc distro to "get around" using TestFlight for external beta testing by using AdHoc app ipa's distriubuted using 3rd party tools like HockeyApp. Is this ok with Apple or not? From what I've read and understand, the asnwer is no - unless you are distributing to your own internal organizatrion (or its affiliates) you must use TestFlight for external betas. For internal betas, you can use Enterprise program, internal TestFlight or AdHoc. Someone pleased correct me if I'm wrong - I really want to get this straight.

Clarification from Apple on Internal vs External users apps for testing
 
 
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