They have quite different return values on what to return when a precise found is not possible. For example, the closest lower returns -1 if it cannot find one, and the closest higher returns 1 + the last index (this saves us another comparison in the calling method).

I can make a mega method, takes one more option to say either returns precise match, the closest smaller or the closest higher, but I think that would make the method a little too overloaded.