the GPL requires source corresponding to distributed binaries be released. They distributed GPL binaries and they have not been required to release the source.
They are allowed to make future binaries which are not GPLed, but the users of the GPLed binaries have not had their right to see the source satisfied.
That's the intent of the GPL (GPL v3 Preamble) but it's not an outcome that a license can guarantee. A copyright license can only be enforced using copyright law, and the remedies for copyright infringement are limited to monetary damages (actual or statutory). Sometimes the threat of a copyright infringement suit may compel an infringer to release their source code rather than be ordered to pay damages, but sometimes not.
A common law contract requires an offer, acceptance, and consideration. That is, one side must offer the contract. The other must accept it. And each must have some potential gain from it (consideration). Both sides are then bound by the agreement. The agreement can be quite complicated, for example it may bind the parties to resolving disputes with binding arbitration.
A license is permission to do something under some conditions. If you break the license, you are without permission. The licensor can then pursue claims against you just as they could if no license ever existed. For example if you break a copyright license, the licensor can sue you for copyright infringement. But without an explicit agreement from you, they can't sue for anything else.
If you want to find a discussion of this topic by a lawyer, a good chunk of https://rosenlaw.com/wp-content/uploads/Taxonomy-of-Licenses... is on exactly this topic. The author of which specializes in open source licensing, and was the general counsel for the Open Software Institute.
Some consequences: (1) the sole recourse for breach of license conditions will be to sue for copyright infringement, (2) only the copyright owner will have standing to sue, (i.e., an intermediate licensee or a user, who might have standing as a third-party beneficiary under a contract theory, will not), and (3) remedies will be limited to monetary damages.