Woups, turns I did still have that code in an active project (and no waitForConversion() command anywhere )… but it was set for a manual button reading.
So I changed it to this, and it works just fine without the delay. Not that I could notice a quarter second delay on a manually called reading anyhow
DS18B20.setWaitForConversion(true);
DS18B20.requestTemperatures();
//delay(250);
Thanks for the knowledgeable info @distans (seriously). I always knew you were full of something JK - the antagonist in me escaped briefly