Impact of export tax- did today's sell off make sense?

It's been interesting to observe the markets reaction to the Chinese government export tax on steel. Theory would suggest an export tax will depress prices and production of steel in China, while pushing up prices and production elsewhere that imported. Indeed US iron ore prices have just opened in NY and held up pretty well compared to today's slump in Chinese prices.

GRR is pretty certain to keep exporting to China I suspect, but a lot of other miners will shift exports to where the price is highest. GRR does occaisionally send ships to Korea and Port Kembla and I wonder what price will be used for those shipments.

A final thought is that theory would suggest export taxes dampen growth and competitiveness. Given the Chinese government has invested massively to initally rapidly grow and in some eyes provide generous subsidies to maintain their steel industry's position, it does raise some questions about how sustainable this policy is? This is not to mention that construction has traditionally been a major driver of China's growth and less steel produced will dampen that.

For what it's worth I topped up today. The thing that prompted me was the enterprise value / earnings multiple being ridiculous, that Vale doesn't seem in a position to push up pellets productionthis year, the thoughts above and Chairman Zhao buying not that long ago. He would likely have seen this coming. If he buys again that would be a big buy signal for me. I am conscious all of this may be confirmation bias talking, so appreciate others views?