The original question actually hasn't been addressed
The RBL seemed to be conceived as a semi-bespoke gun (you had all sorts of options as to wood, gauge, barrel length etc) at a low price which was intended to look and handle a bit like a British game gun.
I'm not sure that the intent was to make a less expensive "British game gun." I've never heard anyone from CSMC state that or anything like that. I suspect, as mentioned above, that it was a way to finance a significant expansion in manufacturing capabilities while
possibly making a profit.
As regards the guns themselves, basically the points, good and bad, are made above.
One exception - the reference to the RBL's handling better than the Parker Reproductions. That could only be due the gentleman forgetting to take the Reproduction out of the case before swinging it! (Just joking!) The RBL Twenty gauges handle fine (But no better than the Reproductions) But the 12"s and 16's handle like oars compared to the Reproductions.
I've had several of each. I now have no RBL 12's or 16's. I've only hung onto the RBL 20's and 28's, but I still have all of my Reproductions.