I don't think the Ultimate makes the law completely illogical. You could make a flintlock strong enough to shoot 200gr of 777 if you wanted to. Inline is just an ignition feature, and a fairly uninportant one with regards to the resulting internal ballistics.
There are only a handful of Ultimates out and they cost a ton. The legions of mass consumer inlines out there are not capable of what they do. If they were, and people were tolerating the recoil they produce, I'd buy into the argument. But the fact is a 200-250gr 777 charge is not something many people are likely to do while smokeless is much easier to do.
My personal feeling is if smokeless is to be legal I'd feel safer with caliber and/or weight restrictions on the bullets. It's just too flat, open and populated around here to be shooting something that truly performs like a .308 or something.
While the Ultimate goes, quite literally, to the ultimate extremes to get 2500 fps out of 777, the Savage will, with less work and a lot less discomfort, get over 3000 fps.