I know how it is used by a few folks, and I've always thought such usage incorrect, confusing, and potentially detrimental, especially for those early in their efforts, but I didn't often correct anyone prior to this because I could 'usually' figure out what they meant by the context of their statement. But this time, somebody actually asked :^)
Actually, I don't like to hear the word 'fade'(out) used on wooden bows at all.... regardless of whether it's being used to describe thickness OR width. I don't use it. It is too often used incorrectly which invariably adds to confusion. When we instruct or converse with GLASS bow builders, 'fadeout' or 'fade' is used to describe the end of the riser... where its thickness 'fades' out to nothing. When it's wooden bows we're building, the narrowed, deep, rigid handle 'flares' out into full limb width, and then 'dips' into working limb thickness just beyond. If the term 'fade' MUST be used to describe a part of a wooden bow, doesn't it make more sense to maintain continuity with the original term... as in 'fadeout'... which describes thickness?
A bow's fades/dips should be beyond its flares. The terms aren't synonymous because they mean very different things, and they're not in the same place. In fact their orientation to one another is vital. Make them the same thing at the same place and the odds of the bow breaking just skyrocketed... which we've seen numerous times. My bows commonly dip/fade into working limb thickness 1 1/2 - 2" beyond the flare of full limb width. Some bows have the dips/fades 3-4" beyond the flares.
Perhaps confusion in terminology leads to confusion in design... which may have something to do with why so many bows break right there.