I think she's trying to make the point that only reason there are still some houses left is because it's a permanent investment.. If SE allowed people to get their money out by selling it, people would be more willing to buy the houses.

I don't agree with the idea, I think opening up the housing market for trade will inflate the prices and have it readily exchanged between people.. But at least it will be available, if the price is right.
Perhaps some people can even make some money by selling fully furnished houses.