FWIW making the chopper lumps and the monobloc integral (out of the same piece of steel) isn't that hard to do and I'd not understand why one would do otherwise. With today's CNC equipment the milling time is only a few minutes to rough in the chopper lumps. Yes it's a bunch of steel to mill away but insert mills do it fairly fast qand a solid carbide tool to finish the sides is not a problem at all.

I can't imagine doing differently. This is not like making a Savage rifle to retail for $400