That is the support structure for the legend (the 1st shot). There are several variations (some / some \ some other), with different properties for supporting legends with different demands. It is normally hidden by the keycap (the 2nd shot) and is chosen according to the needs of the particular legend. With clear 1st shots, and especially clear 2nd shots, this support structure becomes a visible part of the keycaps' aesthetic. One of the things we are working on is to see if we can make them all uniform.