When playing the net, the ready position in the top photo in the OP is ideal. At the baseline, the ready position is much less critical. I encourage students to adopt the ready position shown in that photo so that they already have developed the habit for net play. This ready position creates a mild extension of the wrist -- it should not be too stressed since the upper hand should really be supporting the weight of the racket (so as to keep the lower hand/arm fairly relaxed). This mild extension should facilitate the much greater wrist extension needed for FH volleys. The wrist will assume a more neutral position for a BH volley.
Every tool is a weapon -- if you hold it right. (~Ani DiFranco)