Here is my top rope solo set up. I use a Petzl Micro Traxion. The Micro Traxion is not really meant to be falling onto. So clipping it up to a chest harness is recommended, but this starts to limit movement. So with a hair tie you can keep the Micro Traxion up but still have freedom of movement from the chest harness.
An improvised sling harness can be a useful tool to know for many reasons. The obvious is you do not have a harness and need one. Another reason though could be you only have one rappel on a multi-day ski tour and don’t want to carry a harness the entire way. Maybe you find a stranded hiker (I have actually done this) and they need to be lowered to the ground. Any of the above reasons could warrent the need for a harness like this and trust me, it isn’t that comfortable…
