The +RW Alliance are doing their best to match DVD Forum formats 1 to 1, which has resulted in the take up of recordable DVDs to be very poor, as everyone is confused, the opposite of what happened with DVD Video that had a united front from the manufacturers (due in part to companies like Intel and Microsoft who said they would refuse to support multiple formats, although they seem rather silent about the current mess but have made recent announcements that they are getting involved to sort it out), will the manufacturers ever learn.
The DVD Forum official formats have been matched at a later date by something similar from the +RW Alliance.
DVD-RW then along comes +RW.
DVD-R then along comes +R.
DVD-RAM then along comes DVD-MRW (Mt Rainier although still waiting for these).
DVD Audio and SACD.
Notice the pattern?
The DVD Forum was a nice idea to standardise these formats to allow full compatibility and avoid market confusion, however Philips and Sony have broken away from this in pursuit of their own patents. One reason to steer clear of their formats, they offer nothing very different, and why reward the "spoilt kids" who broke their principals (Philips and Sony were largely responsible for the DVD Forum and the one format at the start of DVD, but then of course they had a lot patents tied up in that so it was in their interest) with giving them your money?
SACD though is not a recordable format. There are no Recordable SACD discs. Can +RW be adapted to allow recording that will play back on SACD equipment I do not know, but bet they are working on it.