While 30 yards is not a very effective hunting range except for tree stands or very dense brush, it's nice to see that some inlines will shoot a PRB accurately. And the groups look like they would probably hold together pretty well past 50 yards too. Similar to the accuracy of a smooth rifle shooting RB's with a tight patch maybe?
I think that it can partially be attributed to the Knight barrel because others have also reported getting fairly good PRB accuracy from them. Maybe it has to do with the depth of their rifling and/or the fairly thick pillow ticking patch?
Since you have so many other models, can any comparisons be made about the Knight rifling and it's depth?

There was a discontinued Traditions .54 Tracker inline model with a 1 in 48" twist that I thought might shoot a PRB accurately but I never did buy one to try it out.
Some folks complain that even the 1 in 48" twist isn't good enough for shooting PRB's, but your report just goes to show that a lot about muzzle loading isn't predictable. 10 degrees cooler or 10 more grains of powder could make a world of difference or maybe not.
But some inlines will certainly shoot PRB's better than others.