While I agree with this, Adobe does have the knowledge and skills to hook a fuzzer into their Flash source on sandboxes and vm's, and basically let a fuzzer rip. When you build one of the most installed pieces of software in the world, you should take that responsibility.
AFL works from the outside (and even accepts certain keywords to "hint" the fuzzer)...so really anyone could run it against Flash having it generate SWF's. But it'd probably take a really long time to find anything.
