What contracts? Is there any major US tech company that has employment contracts? Certainly none that I've worked at.
Traditional employment contracts, which were common years ago but are now used principally for C-suite positions, typically have terms employees can sue to enforce such as WFH.
For most positions in tech, nothing in the paperwork will give you a way of enforcing WFH if the company changes its policies.
That's what I meant by my comment above, which I can no longer edit. (I should have been clearer.)