Maybe it varies state by state. This is what I found when looking for federal requirements:
a place, other than a bathroom, that is shielded from view and free from intrusion from coworkers and the public, which may be used by an employee to express milk
Those do usually need a fridge and sink though. Not sure if it’s a code requirement, but all the ones I’ve seen had that.
Might be why the call it a ‘wellness room’, instead of a mothers room; doesn’t meet the legal requirements.
Maybe it varies state by state. This is what I found when looking for federal requirements: