We practise and train in that style of soft falls. They were introduced to my sensei's in the uk by Mouliko HalÚn from Norway. Since i started three or so years ago they are the only form of over-the-top break fall i have learnt - and i learnt them from day 1. When done properly (i.e not by me
)you can fall from the hardest throw with barely a noise.
In terms of learning, although we have developed a number of practises I am happy to share, I would suggest it would be difficult to learn without finding a sensei who teaches them, as they do take a period to "swap over" to.
I saw Waite Sensei being thrown by Yamada Shihan on tape a little while ago and noticed how similar his falls were to the ones we do - the best option is probably to find someone close(ish) with him on in this style. Maybe someone on here whose US geography is better than mine can help.