That seems like it could easily end up being very slow. The OS doesn't know what data is going to be needed and it could page out the wrong data. It's probably worth trying, but it doesn't seem like a masterful solution.
Of course it was. Because that was better than what we wanted to do, simpler, no development time (cheap , met our deadline), worked well enough. Sure you can get a bit more bang for your buck making a catered-for swapping algorithm, but in the end it does not matter.