You're right Boco, but around here anything movable is called a "drag", a log drag or "clog" is just considered a type of a drag. Yeah they are intended to tire the animal out with weight and cause them not to move far due to that rather than hook up solid in the brush (although they sometimes do), but since they are a "movable anchor" they are usually called a "drag." Often grapples are used here the same as you describe, pre hooked either for speed or ease of setting where driving stakes isn't easy or feasible. I sometimes chain solid to trees rather than use a grapple myself, but the grapple is quicker and easier. Also if the trees or brush within reach of the set are questionable on holding a large animal like a wolf, the grapple gives peace of mind that if they do uproot or break off whatever you have pre hooked it to, they will get hooked up again and not be too hard to find. I can't actually recall anything getting loose from any of the questionable items I have pre hooked to, but I know of a couple that I would never have felt comfortable trusting to hold if I had simply chained or cabled off to them without a grapple attached.
P.S. Every time I set a trap on a grapple where I want the caught animal to travel a ways and get itself hid out of sight when caught, they seem to always tangle up on the first available thing in plain sight. I set a wolf trap a few years ago in an open meadow about ten feet off a commonly traveled dirt road. There was one little lone pine tree about two inches in diameter growing in that meadow along the road. A week or two later I had a friend call me and ask if I had wolf traps down there. A coyote had gotten caught and tangled itself around that little pine tree, the following Saturday I was checking traps and I pulled up just after daylight to a wolf... tangled around the same little pine that I would have never thought would hold a wolf all by itself out in the open. With literally not a blade of grass to hide it from any passerby. So while it is a good plan, don't depend on drags allowing a catch to get out of sight of the public.