I see and understand the argument of restraint of trade however the conditions that he agreed to be released under accepted and acknowledged the restraint of trade for the duration of the contract. This was presented to him, he sought counsel and on their advice signed the release agreement as it stood.
In IR law, where for eg an unfair dismissal matter resolves through mediation or amongst the parties, they will sign a deed of release. Generally that will include a mutual release or similar, a clause where each party agrees to release the other from all current and future actions that might otherwise be available to them.
Excepted from that release are Workers Comp claims (under relevant legislation) and unpaid super claims. Those are tied to other statutory entitlements and cannot be contracted out of for that reason. Workers Comp, for eg (and at a very high level only) is inherent in the definition of a "worker", and you can't contract out of that status because that would be ridiculously open to abuse.
So a person could add those to a release, and it would have no effect. The release, or at least those sections of it, would not be lawful even if the deed was executed and agreed.
I'm not saying that's the case here necessarily, but the point really is that it's not agreeing to and executing a contract that necessarily makes it lawful or binding. Agreeing to an unlawful clause doesn't make it lawful or enforceable, and it's for the court in this case to determine whether it is.
My expectation is that it will, but probably not to it's full extent. That's certainly open to the court to rule.