First of all the Chinese are not focused just on PMs but I would guess that their primary focus is on industrial metals and energy. PMs, but more so gold and silver, are true money to them and it is a part of the ticket towards a world currency. The other major part is for their currency is to be more readily exchangable with others. Trading agreements are part of those steps.

Actually the competition from the west is for the resources but for the price depression of those resources there is little competition if not cooperation.

What price support there is, is for example an iron supplier from Australia, or chromium from South Africa wanting the best price from China.
Just posting my opinion.