For me, flushing really helps swell the calyx and really adds girth to the buds.
IMO, nuits are simply not needed the last couple of weeks at all.
I have ran grows that I have flushed, and not flushed, and the only difference is not flushing just seems to swell the buds a little bigger. It is hard to say if I gained weight or not, just from simple observation.
Another big reason, for me, is running nuits till the end is just wasting nuits.
By "flushing" at the end of a cycle just means I feed nothing but stright water at the end, not a full blown"flush". A full blown flush to me means you run water thru your medium until nothing but clean water comes out.
Hope that makes sense.