Google isn’t their employer, it’s the contracting company. The contract not being renewed is inherently a business decision between two busines entities, which is probably going to result in the contracting company laying off the workers but that can’t be directly tied to Google because…Google didn’t hire these people, they hired a company that happened to employ them.
Is it a loophole? Possibly, depending on the structure of the two businesses in question…but it’s very unlikely to be suddenly declared illegal, it’s been common practice in sectors for a while for basically that reason. Contractors get the shit end of the deal and that needs to be addressed directly instead of pretending they’re already protected by laws.