this is similar to the backyrack type of RTH that has been availablevon some drones for quite a while.
the system just reverses every movement made. the beauty of this type of RTH is that there os no risk of hitting a static object as the drone has already covered that path.
But has the limitation that if you are down to low battery and you were already dashing back to home manually .. there won’t be enough battery to backtrack, and the first thing it will do is dash away from you .. ? 
You are conflating current RTH behaviour with the one described here. No doubt the “battery low” algorithm will be tuned for the beeline nav.
I think this experiment is more for tiny drones, perhaps even bee sized. The memory required for it to work is only 42kb. As the article says:
One of the most promising applications may be agricultural monitoring. Lightweight drones equipped with Bee-Nav could autonomously inspect crops inside greenhouses, identifying diseases, pests, or other problems before they spread. Because the system requires so little processing power and memory, it could enable much smaller, safer drones that can operate around workers without carrying heavy onboard computers.
One area that I can see tiny drones being used is as poliinators. We are facing a crisis at the moment with declining numbers of insects and, in particular, bees due to loss of habitat and the widespread previous use of neonicitinoids. Developed versions of the experimental drones may have to be used to replace real insects.
surely it would be better and cheaper to breed more insects, and stop using chemicles on crops. that to build factories to build ( using mined material) artifical insects.
You don’t necessarily have to pay to breed insects, it’s something they do naturally given the right conditions. But we are busy creating the wrong conditions hence the decline in the numbers of pollinators.
Mechanical bees will be wasteful of resources but may be the only way to maintain our food supply 