That's why I said probably. I just know Monsanto is famous for their "copyright" seeds that are genetically modified and you're not allowed to keep the next generation of seeds.
In this case, Monsanto never sold "terminator" seeds. They (and many others) sold hybrid seeds, which don't breed true, and so are functionally equivalent to that. Hybrid seeds have been around since the 1930s, if not earlier.
In any case, they can get the same effect by contract. You were not allowed to replant Roundup Ready soybeans, and they sued (and won against) farmers who broke the contract to do that.
If the courts cannot see the distinction between farmers and plants violating patents, then the Congress may amend the law to oblige them to see it.