I can see the reasons for some guys choosing this option e.g. after a period of expat work, returning home. However this does otherwise strongly appear to be a back door P2F. You pay your 30k/40k bond get yourself 500 hours on a widebody at half the normal salary and then double or triple that salary going expat, losing the bond.
I guess there's nothing wrong with that but I hate to see this kind of management exploitation.