You know there is so much confusion around this particular point it kills me. I think it would be great if the ball companies would make a unified statement on the matter. If you check Morich they condemn heat treating and favor how water bath (they have the procedure on their web site). Brunswick on the other had endorses the Rejuvenator or Revivor oven approach (the do not recommend using a home oven, you can find their statement in any of their newer drill sheets). Ebonite on the other hand does not come forward and embrace any approach. I agree with the previous statement as to why...they have a "kitty litter" type product that they market.
I also agree with the logic that says, if you have a ball that is "dead" what do you really have to lose by experimenting intelligently on your own. My take from all of this is that when you find 1 or 2 methods that work...use them. It has the potential to save you money in the long run.
Personally, I have used the hot water approach and been successful with it. I have also use my home oven and been successful with that as well. BTW, I also use my own ball cleaner (yes, it is made of all USBC approved stuff). I get great results from that.
So, my opinion is that the devil is in the details here, it could be that certain manufacturers say certain things because of a multitude of reasons. Sure one could be marketing and sales driven. Another possibility is that ball construction materials mat vary between companies and therefore tolerances may be different as well.
Anyway, that's my 2 cents.
Fran