The unemployment numbers are bogus. The Bureau Labor of Statistics (BLS) have changed the way unemployment is calculated so that discouraged workers (people who have been out of the workforce for more than 12 months) or people who have temporary work are not included.
According to shadowstats.com (which is based on the previous way the government calculated unemployment) the real unemployment number for April 2018 is 21.5%. That number seems a lot more realistic, compared to BLS' 3.9% calculations.
If companies started hiring all of those unemployed people, and those people started spending all that hard earned cheap money, it would increase the money velocity (spending, exchanges, transactions), and inflation is going to pop.
If decision makers are basing their needs on the way things are currently calculated, then it is only a matter of time before theory meets reality.
I can't speak on the backlogs, but I can speak on historical events and I can speak on the phenomena of ghost cities. But that doesn't bother people I guess. As long as they are paid in full, none of what I am saying really matters.
Also, there are loads of things they could set off the next downturn. The derivative markets, runaway inflation, interest rate hikes, a spike in oil prices, a terrorist attack, war, etc. It may not impact the real estate market the same way it did last time, but all that artificial demand would quickly dry up.
That is not even being a doom and gloomer, that is just someone who is reporting on stuff that is already in motion.