But centigrade isn’t a measure of absolute units and is disingenuous. Using your argument it requires the consumer/reader to make a number of inferences or assumptions which isn’t a good method of communication in general. It is perfectly valid to say that the cooler took CPU temperatures from 70°C to 35°C.
Why not just say that. It’s an impressive stat!
Scales exist for a reason. Cutting 70°C in half is by definition -101.5°C. But let’s assumed somehow everyone is on the same page and that anything below 0°C should just be ignored in this specific scenario and not any other (confusing right?), saying the temperature was cut in half is still confusing! Half from where? Did it go from 20°C to 10°C? From 80°C to 40°C? It just doesn’t mean anything and as said before I would argue just stating the numbers is more impressive and informative.
All I can say is that in my professional career where I have to write technical reports and summarize technical information I would never represent it that way, and I would be concerned if a colleague, customer, or supplier did it even if they were communicating it to a non technical audience. I would also call out my employer or management if they ever tried to change the representation of the data to something like this.
That could say more about me than anything else, but that’s where I am at.