I completely agree with, Ygirl. I never agree to anything until I have full knowledge of what it entails (is this a long term swap or temporary) and also everyone's intentions, concerns, and feelings.
As to the why of the wife. There have been times when I am not getting my needs met I struggle maintaining our home. Its immaturity and resentment really. Why keep up for those who don't do the same for me. Maybe she needs time to work on her before she can work on her relationship. There have been times where I need me time to figure out if I am being rational or not and to find the words to express what I need. But Im not her and I don't know what issues they are having in their relationship.
Also, if she just needs a break (we all do sometimes) maybe he can stay in your room for a while so she can have the comfort of her own space.