this is not new or original
this "new" method have been used for years...
as for rain water purity, well it might have been pure in early 1900 but nowadays
I don't think it still true.
many tests have shown that rain water might contain chemicals compounds, acids and other impurities that have been thrown in the air by different manufacturing plants, air plains and even natural phenomena like volcano's , and all of this gets picked up by rain and carried down to earth..
that is why in many countries around the world rain water is approved for non-potable use only , as in watering lawns, washing cars/driveways etc.
without extensive filtering and boiling rain water might not be acceptable for consumption.
of course if you live in the part of the world where rain is the only accessible source of drinking water most of the time, you have no choice...
