Now that’s strange…
Maybe you should contact him (or whoever is running his shop) and ask about that.
But yes, he doesn’t advocate self-install, so that might be the case here. My silicone implant came from a German reseller and was sold to my artist, not to me myself, and that was perfectly sterilized - so I guess the reseller did that 
Yeah artists can autoclave silicone no problem but magnets are another issue entirely, and artists use the so called “cold sterilization” method, which isn’t sterilization at all it’s simply soaking in antiseptic solution… haworth does this on purpose because if he indicated his products were clean or sterile and someone got an infection, he would be suspect not the installer… it’s a calculated move on his part to push all legal liability to the installer.
Can’t speak for that internationally, but in Germany, no serious artist does that. They either autclave stuff or use things like e/o-gas or gamma ray sterilization 
I’m okay with that - I expect my installers to use sterile stuff, no matter if it was sterile before they bought it or if they did that themselves. For example, the jewelery my piercer uses comes to him in a non-sterile way and he puts it through the autoclave himself - maybe he just wouldn’t trust “pre-sterilized” things^^
I never trusted pre sterilized things either.
Everything in my old shop would go into the Clhor bath + ultrassound then autoclave combo.
Because even if we trusted the supplier… if anything went wrong along any step in the supply chain, the onus would still fall upon me.
And if something would not be allowed in the autoclave (i.e. magnets or some threads), then just the longer bath on ultrassound was usually acceptable.