The GPL does not actually force anyone to give out source code. The GPLv2 requires to either give out source code to customers, or to give customers a written offer (valid for anyone, not just customers). It is this optional offer, which, being a promise, forces the giving out of source code to anyone in possession of this offer. Failure to honor such an offer is probably not a GPL violation, but a simple breach of contract/promise.
If no such offer was given, then the GPLv2 was violated, full stop. The Conservancy had really no need to ask for source code, since the GPLv2 violation occurred when no offer nor source code was given to customers. The fact that the Conservancy did offer the violators a way out by asking for source code is a pure nicety on their part, since they really didn’t have to.