Seems like a bit of a waste. It is not like they will be able to do anything
with those units when they are given back to the company.. they are not only
preproduction units, they are used units. They'll just sit around the
warehouses until they get thrown away after a few years or the engineers pick
through them as playthings when they get written off. There is really no
difference between giving them units for six months or just giving them away
permanently in terms of cost to the company.
All in all it is a bit odd, but it is still a nice thing to do. And smart.