Woooahh... far from optimal for the yeast
It's not just about "killing" or not killing yeast, it's also about everything that's happening in the yeast. By raising the temp, the yeast's metabolism will go into overdrive. The purpose of life for yeast, is to reproduce itself. To do this, it needs energy, energy is won via the metabolism of C-sources (carbohydrates).
Higher temp = higher rate of metabolism.
What does the yeast metabolise when there are no free C-sources floating around in the medium?
The next available C-sources in it's body/cell.
THIS is the big difference between dropping the yeast into 18°C wort, and heating it up in the container in which it was stored in.
In the wort, the yeast has a lovely rich supply of not just energy sources, but also important minerals and amino-acids.
Higher temps during the pitching phase have many negative aspects either way (more higher alcohols, LESS esthers ---> the combination of the two! A less than optimal ratio of higher alcohols to esters (like all things in brewing, it's not just a matter of more is better or whatever. Think of IBUs vs gravity. Things need to be balanced), an "emptier" tasting beer, poor head retention).
And the even extremer version of this (heating up the yeast before introducing sugars, amino-acids and minerals) is pretty much f**king the yeast from behind in a sauna after having had it in a fridge for a week without anything to eat!!!
It's pretty much a form of forced-autolysis.
People should stop being so afraid of the yeast taking a bit of time to adjust to a new wort. It NEEDS time. It's a completely different medium than what it's been sitting in for the last few weeks.
Be kind to your yeast!
I'm pretty certain that if I even mentioned this idea to all the brewers and brewmasters I know and work with, they'd be so dumbfounded, that they'd probably slap me in the face with beer bottle and never listen to a word I ever said again.