[kenward]

"If you owe the bank $100, that's your problem. If you owe the bank $100 million, that's the bank's problem."

Technically you're correct. If only a handful of employees migrated, they could probably be let go pretty easily. No skin off Facebook's back.

Now if hundreds or thousands of employees migrated, Facebook needs to make a decision whether enforcing the RTO or not will hurt them more. Regardless of technicalities, demanding a non-significant percentage of your workforce to uproot their lives is not an easy ask (or great look).