I have had a bone scan done on myself. A problem is that it can “light up” in areas that aren’t really an issue, or that are secondary issues, while the root cause can remain hidden.
At least with a person it is easier to talk it out to see what they should and shouldn’t pay attention to.
I suppose it may give you better clues as to where to look and possibly show areas you never considered could be an issue, but don’t assume that just because something lights up that that area is painful for your horse.