You are correct of course, many mainstream European branded products are made in China AND provided that's made clear on the product description fine. If tyres are made to the exacting specifications of the main stream manufacturer then I agree they should be of equivalent quality- not the same quality- that's impossible in a different manufacturing plant one reason being their raw material feedstock will probably be slightly different. Its conceivable the Chinese product may even be better than the European manufactured item but since the driving force behind moving production to China is to reduce cost that would tend mitigate against that?
The problem with China is their lack of regulation in the manufacturing arena. This lack of regulation can benefit costs of course but it also makes the manufacturing of counterfeit goods relatively easy. Having bona fide manufacturing plants in China just makes the likelihood of labeling, packaging, identifier mouldings,logos etc going astray IMHO.
Not aware of any "mainstream branded products" being made in China that are specifically destined for the EU market......I may be wrong but we check all countries of origin for all tyres we purchase from various suppliers and would reject any Chinese manufactured "branded" tyres.....they certainly dont come direct from UK arms of the tyre manufacturers, more likely the "grey market" that "hi-jacks" tyres destined for countries outside of the EU, S.Africa being a classic example, whereby the compounds are not suitable for EU climates...when they do appear they are significantly cheaper...and without warranty from the manufacturer !!