You can be fired for any or no reason in the land of the free (see 'at will employment'), so I would guess so.

At minimum it would be nice to require advance notice: "we will require this new employment agreement in 3 months". Rather than the current situation where you must agree now or be fired immediately.

Employment with respect to Amazon or its contractors is an adversarial system. Giving your adversaries time to prepare only negatively effects the companies' ability to extract maximum labor at the lowest cost. Sure some employees will quit rather than sign, but that number is small. Some will sign with the intention of quiting as soon as possible. Amazon still made its money and burns and churns through recruiters and contractors to deal with the turnover. Working for Amazon is like gambling in a casino, the house always wins as evidenced by the stock price.

I was, and I've never worked for a FAANG. I think the excuse was that there was a corporate reorganization so technically we were all being let go by one entity and hired by a spinoff company. So if we didn't agree, they could just not rehire us.