I do not believe Conservancy is arguing contract to the exclusion of license. They are arguing that they can sue under the source code requirement as a promise

I do not believe Conservancy is arguing contract to the exclusion of license. They are arguing that they can sue under the source code requirement as a promise enforceable under contract law. Vizio is arguing that the source code requirement is only a license kind of requirement, so they'd have to be sued in federal court, and probably only by an owner of copyright in the software. The awkwardness in the evidence comes from all the old writing, tracing back to FSF, arguing license to the exclusion of contract.