I am only quoting concerns with several different people I have talked to with regards to "sharpening" blades, particularly on electric motors, belts and wheels, etc. They all said that they were very careful not to let the blades get too warm to the "touch" for fear of loosing the rockwell and softening the blade. Made sense to me...so I don't get the blades that hot either. Besides: It's not needed to clean the blade. I would also be concerened with the plastic fiber spacers with too much heat.
None of this may matter at all...but I'm going to follow their theory. I did say "others" may have other ideas. That's fine. I get the shop-installed grease/wax composite off of the knife without over-heating the water just fine. That's all I'm saying. I will also add that too much hot water also takes the nice shine off of the handles as well.
Everyone has their own ideas. I know that mine work and I have used this method on Randalls for many years, many, many hundreds of knives with no ill effects.
Best, Capt. Chris