Writeback bug or feature in SSAS 2008 R2

I wrote on my last project a .net desktop application used for forecast and monitoring in contact centers as reflected in the blog entry 'Cube writeback with multiple values in one shot'. I won't reveal all the details of this application but it is based on OWC on a windows form, cube actions intercepted in events fired when user invokes a context menu and finally writing the changes to the cube. You may recall that cube changes are not written directly to cube cells but to a relational table called writeback table.