It is interesting , if true. The question isn't whether a new congregation would be eligible ( I suspect it would ) , it's more whether the Society feel there is any need for it to register as a charity. The only benefit would be that the congregation could claim gift aid on donations - presumably with the new system whereby virtually all donations go direct to WTBTS or IBSA ( both of which are registered charities ) then there wouldn't be any particular advantage in the new congregation registering.
As very few new congregations are formed ( if anything , they seem to be merging ) , I wouldn't have thought that there is much of an incentive for the society to get the few new congregations to apply for charitable status. They now have to demonstrate a "public benefit" which has caused problems for some religions , like the Bretheren http://www.eden.co.uk/blog/law/brethren-church-denied-charitable-status-p11199
I also wonder whether the Charities Commission increasingly getting involved in the Societies affairs ( eg the investigations into recent paedophile cases in congregations in the UK http://www.charitycommission.gov.uk/news/charity-commission-investigates-jehovahs-witnesses-charities/ ) whether the Society think that there is really much point in new applications.