It causes extra stress on the engine components. There used to be cooling issues back in the 80's and you had to cool the car down for 2 minutes before turning it off. I think this is states in the NX200t owners manual too, but dont know how relevant this actually is in modern engines.
There was a lawsuit against BMW for the N54 engine back in the states. They had to put the car under warranty for 10 years/120k miles as it had pump issues.
No manufacturer worth their salt would produce an engine that over stressed components nowadays. Things have moved on considerably since the 80's, particularly on the design and manufacturing tolerances side. Look at all the Mitsubishi Evo's (FQ300's and FQ400's as an example) and Subaru WRX's out there that have done many thousands of miles with no hitches.
This engine looks quite interesting to me, and i'm curious why they have gone for an air to water intercooler as that introduces quite a lot of weight, but maybe in a less sporty car like the IS weight is not the biggest consideration. I'll be interested to test drive it when it is launched.