Speaking as an owner of a double chambered in a rimless cartridge...you're completely correct: it doesn't seem right!
Nevertheless, it's functioned perfectly for the roughly 750 rounds I have through it. Nobody ever seems to express disapproval of Ruger chambering rimless cartridges in the #1 single shot, and I never hear of a failure caused by this. Dyed-in-the-wool traditionalists always claim that eventually the rimless round will inevitably slip behind the extractor and cause you grief. I've never seen it happen, either with the hundreds I have fired in the Merkel or the several thousand rimless rounds through a bunch of #1 rifles over the years.
The Baikal allows adjustment of horizontal dispersal only. You can adjust the vertical to an extent but you will be messing around with feeler gauges and shims, and it isn't a quick or simple process. Once you get it the way you want it, you will not want to change it. I found that the easiest way to get the Baikal to shoot both barrels to a single POA was to just sell it and buy another one! I had a couple before I got one that was coincidentally shooting together on one horizontal plane; after that the built-in adjustable system made it easy to bring the two barrels together. I actually flowed some solder into the barrel yoke at that point to keep things solid.
The Merkel has a very cool system that allows adjustment in both horizontal and vertical planes. It's not quite as simple as adjusting a scope, but generally speaking you can get very workable results with only a box or two of ammo expended in the testing. Each barrel by itself is an easy MOA shooter; once you refine the adjustment and get it perfect, you can expect composite L/R groups of 2 or 2.5 inches at 200 yards. I have mine set up with a 180gr bullet load that will print a 4-shot group, L/R/L/R, of 4 inches at 300 yards. If you wanted to, I would wager that you could adjust it so that the two barrels were sighted dead-on at two different ranges; I'm not really interested in that type of set-up but I can see where it might be useful. It's a bit of a shame that this DIY regulating system is only available on the small-frame Merkels, but I suppose that there isn't a real need for it in a true big-bore with limited range.
Once you add in the Merkel's excellent triggers...the front (first) trigger is also a set trigger for extreme precision, if desired...the small-bore double is about as versatile as most bolt guns for typical hunting distances, say up to 300 or a bit beyond. Not what you typically expect from a double rifle.
