Under the old law an unpaid contractor or subcontractor could walk off site, subject to serving the correct notices. But it was not done often because of the risk of damages for repudiation if you turned out to be wrong. The new Act gives the right to suspend part of the obligations, not just all. Much less risky. Just threaten to boycott the site meetings. Same if you’re an unpaid architect or QS. Plus you can get EoT and costs for it.