He's been reported to the Advertising Standards Authority numerous times for this very claim - but as of yet, they've failed to take action on this one.
I strongly urge you to also report it to the ASA too then multiple reports might get something done about it.
It's misleading and, potentially, fraud too because its obtaining money by deception.
Hi. I'm a gemmologist, qualified with the Gemmological Association of Great Britain over twenty years ago. I stumbled across this thread while searching for something else.
It's unlikely that the Advertising Standards Authority will do anything about any such complaints, for two reasons: firstly, jade is not at all well understood in the west, and secondly, the very term 'jade' is an umbrella term for a number of materials.
It used to be (broadly speaking) just jadeite and nephrite, but recently other materials have been deemed to have characteristics that qualify them for a place under that umbrella, too. Dulong jade is one of these 'new jade' materials (a quartz-based material formerly called Du Long Yu) not always considered a jade. but now it is. Similarly with quartzite, and specifically that from Burma - which, since 2013, laboratories in the East have begun to certify as a jade.
Now, challenging that will be difficult as the East understands jade far better than ANY laboratory in the west. I'm aware on at least one Gemporia customer who (like you) was suspicious, and took her purchases for independent testing at a very well-respected Western laboratory, where they were independently confirmed as jade (at considerable cost to that customer).
It helps if you understand that gemmology is not a science that can always give answers in absolute terms, and traditional gemstone definitions are changing as the ability to test becomes more advanced.
But seriously, no worries. I actually 'learnt' that (the quartzite thing) when I was a relative 'novice'. And now I'm a qualified novice 
