Unconventional is anything that is not underwritten in a conventional manner. A situation where you inherit a property and take out a mortgage to pay out others with shared inheritance in a property is almost certainly not representative of the underlying reason for the growth in the 3%. If the author is trying to imply a rebirth in reckless lending that caused the last recession then I'm arguing they picked the wrong subject. If it's because they couldn't actually find a subject that definitely should not have been given a mortgage then the entire premise of the article is wrong.