My idea of a specular highlight is direct sunlight hitting polished chrome or other metals or glass and it is intended to be printed paper white in the print. The zone system or BTZS incident methods are intended to cover the range of tones from jet black in shadow to titianium white in direct sunlight. This is more than adequate for a full range print going from maximum black to paper base white. Another good example would be the intense scintillations on sidelit or backlit water that are in direct sunlight. If you tried to print them other than a textureless white with any system I believe it would be very difficult to do and would end up with a very strange looking photo. What would one expect to do with something that reads zone 27 for a brilliant, intense specular highlight(s) for example when you have skin tone that you wish to have at say zone 6 1/2?.