At 5'-6" or 168cm, with an 83cm inseam and 73cm saddle height, I have long legs and short torso. I use a 25mm setback post with the saddle further back than the midpoint. I also use a fairly large saddle to bar drop of 10cm. That requires no steering tube spacers and a -17 stem. If I have a frame with a reach that's in between stem sizes, I choose the shorter 100mm stem and push the saddle back further rather than use a 110 with the saddle further forward. I do a lot of climbing and the further back position works better for climbing, IME. Part of the post setback is due to the steeper STA of 74-74.5 degrees, used on smaller frames. I could even use a frame with a 75 degree STA, in some brands. That would require a 32mm setback post for me.

The forward positions on the pro bikes are accompanied by a large saddle to bar drop and long reach, similar to that of a time trial bike, but without the aero bars. With the vast majority of cyclists not competing, pro positions aren't all that relative to the average Joe cyclist. Most would find the position to be uncomfortable.