You can't force people to pay taxes either, but that doesn't mean it is legal.

What Mnunchin verbally says is not necessarily what is required.

The Chamber may appreciate "reports" that is optional, but "reports" mean nothing.  Until there is official guidance, it is still not a definitive thing.

I also think it is interesting that 7.8 billion people know what to do and follow Mnunchin, when it seems like most tax preparers in the US are not sure yet due to the lack of official guidance.