I honestly don't feel like that is new. The residential side of underwriting has boiled down to, "verify income via tax returns/W-2's/etc., check DTI (generally looking for 40% or under, although varies slightly per bank), either approved or declined.".
And I'd be willing to bet that a solid 50%+ of American's have been buying as much house as they could get approved for decades now. That is pure speculation, but it wouldn't surprise me one bit. The McMansions of America are not a new phenomenon. The biggest difference right now, is that the vast majority of people are getting less house for their 40% DTI than they were 1 -2 years ago.
Edited to add: The bumps in the road become less and less relevant as banks are quick to forgive payments, modify loans, etc. to avoid dealing with the massive REO problems of 2008 - 2012(ish).