I'm brewing 6 lagers right now (all Wyeast 2206) according to the Brülosopher Fast Lager Method. Essentially, it involves fermenting at normal lager fermentation temperatures until it is 50% attenuated, at which point the temperature is increased to 65°F/18.3°C over 36 hours "until fermentation is complete and the yeast have cleaned-up after themselves". The temperature is then dropped to lagering temperatures and is kegged/bottled only 3-5 days later.
I've only tasted 2 of them which are undergoing the diacetyl rest at 65°F/18.3°C, but I did not detect any esters or off flavors at all. Granted these are my first lagers, but I also have two pale ales that I accidentally fermented at 78°F/25°C for the first 1-3 days and I can noticeably detect esters and other off flavors there.
Given the optimal temperature range for lager yeast tops out at 55°F/13°C, how come this method does not produce off flavors or esters? I assume it has something to do with the fact that the temperatures are not increased until the lager is 50% attenuated, but I do not get why the yeast would only react poorly to higher temperatures if the wort was less than 50% attenuated.