Regardless of the fact that, current Google pictures now shows taxiway shoulders, the concrete usable area is still 18 meters, as in the scenery. So, the issue, it's not that the taxiway is too small to be used, because it's exactly like it is in reality.
Having the shoulders added would be only a cosmetic issue, since you are not supposed to used them for taxiing anyway. The only issue would be the 3d taxiliights, that should be placed along the shoulders but, sorry to say, this (on top of updating the ground textures) is not the kind of update that it's easy to do.