I think what we are seeing here is the RA strategy of focusing on keeping the top 30 players, and 30 developing players and letting the middle tier sort itself out. We don't know the details of the contract yet but perhaps it just a one year deal and with the uncertainty around the comp for next year, let alone any test matches, it's not a stupid move by them. Kellaway is probably close to the Wallabies squad this year but I'm sure he would have worked in a break clause.
EDIT: Twitter inferring that it is just for next season (Jan-May) so they could feasibly play for the Wallabies this year, do the Japan thing, resign with an Aussie franchise and be back for tests next year.