When an observer watches the expansion of mercury up a glass tube, and compares it against a calibrated scale, is that pristine? Or when a thermocouple output is fed into a microchip, which measures the voltage and compares it to a lookup table, feeding the results to a display driver to show, is that pristine? What about when infra-red radiation falls on a sliver of silicon orbiting hundreds of kilometres in space, causing the electron charge to change in a quantifiable way across a tiny set of squares, which is then measured, digitised, compressed, transmitted and reassembled into a satellite picture on earth, is that pristine?
Part of ensuring good data is removing obviously incorrect values, if a digital weather thermometer was showing -255.0 degrees the obvious conclusion is that the thermometer has failed, and its output should be disregarded. The conspiracy theorist conclusion on seeing the removal of that data is that the Bureau of Meteorology is following the age-old three step plan - Step 1: Remove cold weather readings to create a false impression of a warming planet and prevent pilots from loading their aircraft to its full capacity, because they really, really don't like pilots. Step 2: ????? Step 3: Profit.