I suspect that if the REM export controls are going to be removed, it would be de-emphasized and implemented under the table. Chinese domestic social media is in a furor over this announcement because it's seen as a capitulation by China, having the REM control removals additionally explicitly announced would cause an uproar.
In practice, 30% tariffs is extremely high (though the discourse around 145% tariffs have superficially cognitively primed people to view it as somehow insignificant when in material terms, the difference is not huge). Getting this agreement is a "success" for China on technical terms though it does entrench all these artificial Trump 2 tariffs as the new normal. 30% is catastrophically high, but not apocalyptically high - meaning that many US export oriented sectors in China will be able to scrape by rather than collapse (though the de minimis cancellation doesn't seem to be reversed at this moment).
The issue lies in perception. Getting slapped with 30% from the adversary and having your own side reduce retaliation to an unreciprocal 10% is bound to be spun by the Trump government as a PR win. We should be past the point in time where China still allows the US to make these kind of face-saving agreements and the bilateral relationship should have been developed to be in a position of tit-for-tat equality by now.
The Chinese side should be faulted for its messaging. Getting the entirety of society cognitively primed for a protracted economic war and total decoupling while suddenly presenting everyone with the fair accompli of an agreement is one thing (encountering this kind of whiplash is actually exasperatingly common in PRC history like the US normalization process in the 70s) but the negotiators at this talk were literally making public statements saying that "these are just preliminary talks and not to expect an agreement" during their intermission break.
Going from a stance of "never surrender" and "China emboldens the rest of the world through its example" to suddenly binding itself to - what seems on the surface as - an unreciprocal agreement like this along with the inevitable Western media and White House spin about how the 30% vs 10% differential means "China was desperate after all" is bound to be messy. For Trump and the US media, this will undoubtedly be spun (as the stock market reaction shows) as a win that will compel other countries to come to the table for tariff negotiations.
For China, pulling these kinds of moves damages domestic confidence that one's individual position aligns with that of the country's. There are still articles on Guancha by authors telling people to expect a "protracted war" and "no agreements" published immediately on their feed directly below this announcement's. Once again, Chinese domestic media is likely going to fall in a position of never taking any strong stances and perpetually hedging because no one can predict their country's position won't suddenly change.
More importantly, this agreement shows that China is not prepared for an economic showdown with the US or its hegemony at this time. This was a rare opportunity for decoupling on entirely Chinese terms where the US culpability means that China could not be blamed for any measures it took in response. It would have been undoubtedly painful but it would have forced Chinese economic production to undergo the cold turkey-style painful transition to internal circulation and Global South reorientation with the least amount of resentment towards the government through the US having unambiguously incited the entire confrontation and firing the first shot.
Whether based on top level assessments of the material conditions of China's economic dependency on the US or just lobbying pressures within the CPC, it shows that China is still constrained by its reliance on the existing economic order.