I think somebody is telling porky pies
Imagine if you were in icing conditions and needed to apply carby heat at a critical moment in flight such as a missed approach?
I doubt any Pilot would find an 800-1000 rpm loss acceptable unless it was due to icing in the carb which was starting to improve quickly with application of heat.
Something tells me that the average GA aircraft with 800-1000 rpm lost would struggle to get airborne let alone fly! (think about 2500 rpm - 800/1000 rpm = 1500/1700 rpm) this is a typical decent power setting for a fixed pitch machine.
Sometimes it's hard to teach someone something when their glass is already full.