A home exchange, even when Guest Points are involved, is a commitment. When someone cancels, they are breaking that commitment. If there is a legitimate reason, the guest should inform HE so that the guarantee can be activated and HE can refund the points. Otherwise, it is not the other party’s responsibility to bear the consequences of a change of mind.
Therefore, if someone cancels their stay in your home, you have no responsibility for that decision, and not only are you not required to return the points, but, in my opinion, it is actually better not to do so. Otherwise, people may start behaving as they do on rental platforms, where the use of “free cancellation” has become increasingly common.
The further we stay from the vacation rental model, the better home exchange will work.