There is a head company called 7 Nation which has a number of sub brands including Slingshot and Ride Engine. It's a bit like
Boards and More (Fanatic, ION, Duotone),
Pryde Group (Neil Pryde, JP-Australia, Cabrinha, RRD...) in the windsurf market or
LVMH (Dior, Kering, Louis Vuitton, Moet etc) in the luxury brand market.
7 Nation is probably the head company that probably owns the intellectual property which are then marketed under different brands. For example this allows Slingshot to take it's discontinued foils and sell them under a different brand name (eg RideEngine). I have read on a US forum that Slingshot is about to release a new range called the Phantom Foil. This would explain why they wings are now sold by RideEngine. I have also seen a video with Logoz saying he will send the foil designs of the current range to anyone interested.
As far as manufacturing is concerned I am guessing it all comms from the same factory in China. Again the contracts with the Chinese manufacturer are probably negotiated through 7 Nation to get more leverage on price.
More about it 7 Nation here:
www.thekiteboarder.com/2015/05/ride-engine-joins-forces-with-7-nation/As far the Chinese designing a foil without the help of a dedicated foil test crew... I wouldn't touch that with a 10 foot pole.