I'd add that your problem with the cake was a problem with the cake, not the water. Your cake was soft and crumbly. I've never lost cake from this, though in fairness, I keep cake to a minimum, and what is there is hard and clean.
Burley blends tend to make soft somewhat porous fluffy cake, unlike the hard shiny glass-like cake often seen with Virginia. Even with 1/16" of this cake it was becoming softened and sticky enough to have the paper towel leave bits in the bowl. This is something I've never had occur prior to using this method.
Fills dropping out in the chamber? Badly filled. Shouldn't be a problem at all unless they're quite deep. Cake will form over them in time. Or was it exterior fills?
It was an exterior fill. I knew the fill was there, but it was hidden well enough in the blast to not be obvious at all.
The fill had been totally stable until I began to submit the pipe to hot water rinses. The wax softened, and likely due to the blasted surface there was enough unsealed areas in the pits to allow water to soften the fill enough to fall out.
Now, for any given method espoused as "better" and/or "harmless", the effect of using it would need to be the same or better in cleaning, and the same or less harmful than whatever process was used before it regardless of other variables. You can blame low quality cake, but I never had a single issue with cake doing this prior to hot water rinses. You can also blame a low quality fill, or that the pipe was blasted and had a improper or insufficient wax job for the failure - but given that the fill was stable, and the wax job wasn't even remotely an issue prior to hot water rinse, that too doesn't necessarily stand.
I am not saying that this method doesn't clean or doesn't have any merit, because it does certainly clean better than a plain old pipe cleaner alone. What I am saying is that it is not necessarily going to give desirable results, or even be totally harmless in comparison to more traditional methods. I am just providing those looking to try it with my experience, which on some pipes was good, and on others really not good.