Yes, there are differences in opinion and methods. I have used this for 150 Hagi (last count) without any problems ... and I am quite careful ... er A.R. about it.
Placing the Hagi in the water when it is just warm and making sure the water never boils is critical. No moving or bouncing Hagi.
However, pretreat how you like, like how you pretreat.
Interestingly, sellers have included info stating to place your new Hagi into boiling water for hours. And leaving it in the water for 8 hours.
I have left pieces in hot water that never boiled for up to 8 hours, this was vintage Hagi that I think sat around in its box for many years and it took 1-2 of these treatments to get rid of the extreme earthiness. I actually have to retreat one set for a 3rd time before I use it again.
IMHO and in my experiece, the more porous the Hagi piece, the more treatment it may require. Follow your nose!!!
Also ... after each use, I fully dip in very hot water and towel dry. The hot water will heat the Hagi clay so it will dry out much quicker. I actually have a pot that I have on the stove all the time, it is reserved for teaware cleaning. I then recycle the hot water for other uses. (Tokoname kyusu dry much better with this as well)