Both handle types being discussed are "cut down tangs, i.e. no "exposed top or bottom. All leather CDT's have a full tang (length-wise) to allow the threading of it and the nut to tighten it.
CDT's with out a butt cap extend into the handle at various depths, depending on the blade thickness, model #, maker at the time and "drop" etc. of the handle material. I think, as a rule, you could approximate 1/3 to 1/2 way through the material. Hope this helps.
Capt. Chris