Hello,
I understand your concern. However, please do not worry about the news. It's understood differently inside of Japan.
Airbnb was never clearly legal in Japan up to now, though Japanese government is trying to accept it for rapid growth of tourists visiting Japan and never tried to discipline it.
This time, the law is more to ease the restriction on Airbnb hosting because it's now at least accepting Airbnb with more than 6 nights restriction where it did not permit no matter how long the stay before.
So please do not worry about your trip to Japan and accommodation. ^^
Kiyoko