That is not what the contract says (at least from the current lawsuit). Amazon has to formally give a notice that gives them 30 days. Amazon telling Parler that they are violating is not in accordance what most people believe the contract says.

Now it's possible that the contract has some other wording, or that Amazon will argue that they didn't need to be as formal as Parler thinks. But as this goes through the courts, we will find out more.

You don't have to guess about this. The judge cites the AWS terms in the ruling. AWS was not required to give any notice under the circumstances.