As some here have shown it is easy to think of a turnback as simply a 180 degree turn. It will always be more than 180, and the worst case, close in, is nearly 360 degrees of turning ie 270 left then 90 right or vice versa. Think of the height loss to accomplish that, not simply to turn 180 degrees.
Minimum height loss in the turn was achieved with maximum practical angle of bank. Turning increases the stall speed, and the stall speed in a steep turn will most likely be greater than the normal best glide speed You're already low, struggling to make it to anywhere suitable to land, there will be a tendancy to want to stretch the glide and reduce (transiently) rate of descent and yet to make the turn the nose must be stuffed further down, the speed increased and rate of descent increased whilst aleady rapidly closing with the ground. Add in to that a bit of disorientation from looking at ground references when there is a wind component and the stressed pilot may tend to fly slightly out of balance.
All this puts you in prime stall-spin-crash territory which has bitten even the best. Not a nice place to be.