For example a gate... select each end of the gate and a Gate Symbol is created based on the two points and scaled correctly. Another example is a rectangular service box or grate, two corners (diagonally opposite each other) shot in the field and the symbol is created and scaled (x & y) correctly based on the two corners.
Alternative tip that can be used in the meantime: You can also scale by mouse by selecting the symbol, holding the SHIFT key and grabbing the top right anchor (cursor will change shape to arrows) to scale X/Y. You can also grab the other anchors (holding SHIFT) to scale X only, Y only or rotate.