I have/have owned .22 Ballards by Eric Johnson  (6 & 8 groove), CC Johnson, Pope, Peterson, Neidner, and others that are unmarked. Every single one of these had match chambers that engraved the rifling on the bullets. The Hubalek is the only one that didn't.

The "mini-Ballards" were actions put on guns that were sold by Arthur Hubalek. They looked just like a standard ballard action, but were smaller size, about 4/5. They had hammerless/striker breechblocks. They were attributed to Hubalek but were likely made by a man named George Worn, who was a gunsmith in Maspeth, NY (on Long Island).
There's more detail on them in the Dutcher Ballard book.

From what few I've seen of the "mini Ballard" actions, I'm not certain they are truly a scaled down version of the original Marlin Ballard. They appeared to have material shortened on both ends of the action to make the overall length shorter. But the central part of the actions seem the same size as regular Ballards. Just shorter in the thread section for the barrel, and shorter in the tang section. They also had a shorter tang screwed into the action, and of course Hubalek's striker breechblock.