If the ITC finds injury, then dumping duties are assessed. If no injury is found, then the case is over, until the ITC gets sued, which is all the time. At any time during this investigation a couple of unusual things may happen. First a US petitioner can request that the investigation be terminated. This is rare.
Commerce can also suspend an investigation.
The matter is merely suspended because the threat over these foreign firms head, like the sword of damocles, is that the investigation will start up again, or that duties will be imposed. These agreements must be capable of monitoring, and be capable of monitoring, and must be within the public interest. What is going on at the Customs level during this time. Customs' job is to oversee the entry of foreign merchandise. Foreign merchandise when entered into the customs territory of the US is charged whatever duties that may be due on the product.