Of all the rare earths. The most valued appear to be those used...

Of all the rare earths. The most valued appear to be those used in permenant magnets and EVs
The thought that China is trying to keep a stranglehold on all REEs resources around the globe, is, I feel, slightly outdated.
Perhaps a decade or two ago this may have been apparent when MP fell to pricing wars. But given the rise in demand, China becoming a net importer and western awareness and restriction on Chinese investment in these sectors. Id think China knows it can no longer keep a lid on it all for obvious reasons.

Chinas control has moved to a new space in the finishing process of REEs into permenant magnets. They currently conduct 90% of the worlds finishing process.
"Powerful magnets made of rare-earth minerals are essential components in electric-vehicle motors, wind turbines and other technology. China mines over 70% of the world’s rare earths and is responsible for 90% of the complex process of turning them into magnets, analysts say. That dominance gives Beijing sway over makers of various fast-growing technologies.....“For these minerals to go from a hole in the ground to an electric motor, you need vast skills and expertise, which barely exist out of China,”"
https://www.wsj.com/articles/u-s-faces-uphill-climb-to-rival-chinas-rare-earth-magnet-industry-11618133603

China have been making massive inroads into buying up control in this sector more than the resources themselves.

"As the United States pursues China up the rare earths value chain, it is finding that each segment poses its own problem all the way through to finished product.The country currently has virtually no capacity to produce neodymium-iron-boron (NdFeB) magnets, the most common end-use application for rare earths and one that is set for exponential growth as the global automotive industry migrates to electric vehicles.Ironically, General Motors, which held one of two original patents for such magnets, sold the rights to China. Japan’s Sumitomo sold the other to Hitachi, which is now the primary supplier outside China.“China is where most magnets are made,” Pol Le Roux, vice-president of sales and marketing at Lynas Corp, told Argus Media. (“Argus White Paper: How to build a rare earth supply chain”, July 2020).“So where do we expand? In the U.S. and Europe? But there is very little magnet manufacturing there. So if we make more oxides, the only customer is China,” Le Roux said."
https://www.reuters.com/article/us-usa-rareearths-ahome-idUKKCN24T20I

China already have control over the REEs that get sent to them. Why really do they need to own or control all the rare earths projects around the globe too?

China have been wanting to step foot into Africa for a long time. In fact many countries. All via their Belt and Road iniative. I think they would be happy enough having achieved that task into Tanzania, with some difficulty as we see, to then want to risk over stepping the mark and start targeting companies that they already hold indirect control over down the line anyway.