Here's the deal with the monolithic design:
Cowitnessed optics, magnifiers, NVOs ,etc.. benefit from the monolithic rail design in that they will consistently return to zero and not be subject to POI shifts that can result from the forearm losing it's thread tension at some point. This is one of the reasons the SPR platform featured a monolithic rail that spanned the receiver and forearm. On the whole, it's a much more rigid platform than receivers that utilize thread tension for rigidity.
In any case, to each their own, but I sought this platform out to see how much accuracy I could achieve and the monolithic design has so far yielded the best results in that regard.