These questions indicate a misunderstanding of how markets inside China work. I suggest you don't look at "what makes sense" but more look at the reality of what's happening.

What you are also missing is that sometimes, parties are not allowed to abandon ship. Couples who have bought homes with mortgages but are not moved in for years are not allowed to give up, they are not allowed to stop paying on threat of imprisonment.

The organizations on the countersign are also not allowed to give up on mortgages because the existence of their company is at the will of the government.

There was an uprising where people banded together and just stopped paying their mortgages and basically threatened the local police to mass arrest them, and that's one of the things that spurred the greater bankruptcy, because the government didn't really want to arrest all the people, cause that would indicate they are not in control. And seeming to be in control is what the government will opt for every single time in every single decision they make.