Umm, yes, I see what you mean. Looks like the first checkin was 66 lines, but it's grown a bit. I think 11 or 12 lines fall away if you remove the conditional compilation, but it's still over the 66 lines. It's a big page.
I had another look at what revalidinho said... it's the assembly code which comes out cleaner, is perhaps what I missed. So, OPC5[LS] is a smaller machine, OPC7 is a nicer machine to program or have a compiler target, and OPC6 is somewhere in the middle.
But great work in condensing the OPC6 in nMigen down to a page!