Imo, it's always been a PR stunt..... and has always been up to the host to decide whether they want to host first responders or not, whether they will charge normal nightly rates or not, whether they will host first responders as a sort of contribution....... even in the best of circumstances, Airbnb never provided much protection to hosts and they never will.
If I wanted to donate or give back to my community in any way.... as a host or otherwise.... I personally would not do so thru Airbnb.