I'm a bit confused by some of what I'm learning from discussion threads and policy documents.
The proposed FlexUnit source release includes source code that originates from Adobe under BSD. These source files have not yet been donated to Apache.
A recent thread says that for a source release, the BSD license does not go in LICENSE and the BSD license requirements are satisfied by the BSD license and copyright in the headers of these third-party files.
Pointer to the discussion? Based on your description, I would disagree.
Meanwhile, the Licensing How-To  also says: "In LICENSE, add a pointer to the dependency's license" but the paragraph seems to be referring to dependencies that are essentially entire libraries, consumed untouched. In this case, FlexUnit (version 4.x) is a next-generation, mostly re-written version that includes a subset of the Adobe BSD files. In the current release candidate, the fact that there are Adobe BSD files in the distribution is not mentioned in README, LICENSE or NOTICE. You won't find out until you open one of the Adobe BSD files.
"Dependencies" may be more the norm, these days, but the instructions still hold.
Personally, I prefer to see the license in the LICENSE file (and not a pointer). However, if the licensing information is made clear to our users and we're meeting the terms/requirements of the ALv2 license and any other license that is part of your release, then all is good.
A related question is: is a "dependency" the same as a third-party work? IOW, are the Adobe BSD files in the source kit that are also checked into the repo still considered a dependency?
No. IMO, "dependency" refers to software that is not directly part of your project.