I've heard the same thing. Word is that many of them are made by Masterworks. Not the Istanbuls - both Mehmet and AGOP have their own manufacturing. But I've heard that at least three of the others are all Masterworks that have been re-branded. Not that it makes them bad cymbals mind you.
I'd consider the Istanbul Mehmet/Agop/Peras to be in sort of a different class than these newer companies. Soultone had Masterwork as an OEM at one point IIRC, though an angry man on the internet told me that they've since gotten their own foundry. He said that someone at the company told him via private email so he couldn't show me a source. Make of that what you will.