Okay, so you have a bone where you want individual control of each finger bone/knuckle, but you also want to manipulate something that curves all the knuckle bones at the same time?
Iām not totally up on terminology, but I would consider anything that did that to be a ācontrolā as well. Because, well, itās something you use to control the way the mesh deforms.
The way that Iāve seen Blender rigs named, basically anything that the animator interacts directly would be considered a control. A bone that actually deforms the mesh would generally be called a ādeforming boneā and a bone that does neither (to kind of modulate controls, like changing a pivot point or marking a tail you want to track or something) would be called a āmechanismā bone. Note that a bone could be both a control and a deform in a simple rig.
In your example, the way that this would likely be done would be, youād have all your knuckle bones copying offset local rotation from a different bone (taking care to set knuckle bone axes, and generally assuming youād only be rotating in a single, well-defined, possibly transform locked axis.) The knuckle bones could be simple control+deform bones, they could be controls that were copied/inherited further down the hierarchy by eventually deformers.
In 2.8, yeah, itās a pain to move from an armature to a different type of object; in previous versions, it wasnāt nearly as painful (barely painful at all, and I donāt personally understand why they changed it.) However, think about if you took a simple five-bone skeleton, all bones are deformers, and gave each bone a child-of targeting an empty. Youāve created a structure where you no longer have to interact with the armature at all. Essentially, the controls for your deforming bones are all empties.
Thatās the simple example. But think also about how curves can be controls-- you can shapekey your curve, which shapekeys a spline IK chain of bones, you can hook your curve, from any controls you want for that hook.
Or, with shrinkwrap constraints, even the shape of a mesh can be a control, that can be used to tune interpolation curves or angle limits, and can interact with other objects via modifiers like booleans (or of course shapekeys).
There arenāt really any rules for how you want to control a mesh. What matters is who you want to animate your model, and how they like to work. If they expect bones and only bones, then itās smart to give them that. But if theyād prefer to never have to enter pose mode, and you as the rigger want to indulge them in that, itās entirely possible.
I did see your other thread-- Iām not sure how to answer it, except that yeah, Blender constraints havenāt always worked the way that I expected them to. I think part of that is that they transform rotation into Eulers which isnāt a great thing to do, but they also donāt seem to do a great job of keeping track of local axes throughout the entire constraint chain. I canāt answer your question about whether itās a bug or what, but if you were describe in plainer English what your end goal was, I might be able to help with achieving that goal. (Just be warned, sometimes rigging solutions in Blender are more complicated than it feels like they ought to be.)