First of all, lets take a look at the initial announcement made by the EU in regards to reopening borders. This happened on June 30th 2020, long before vaccines were available anywhere in the world. The criteria set out for reopening the border were:
Regarding the epidemiological situation, third countries listed should
meet the following criteria, in particular:
number of new COVID-19 cases over the last 14 days and per 100 000
inhabitants close to or below the EU average (as it stood on 15 June
stable or decreasing trend of new cases over this period in comparison to the previous 14 days
overall response to COVID-19 taking into account available information, including on aspects such as testing, surveillance,
contact tracing, containment, treatment and reporting, as well as the
reliability of the information and, if needed, the total average score
for International Health Regulations (IHR). Information provided by EU
delegations on these aspects should also be taken into account.
Reciprocity should also be taken into account regularly and on a
Now lets take a look at the graph of cases in China vs the EU from January to June 2020, adjusted for population:
As you can see the number of cases in China has been completely flat after the initial outbreak in Wuhan. On July 1st 2020, the EU was reporting 4000 cases per day vs just 12 in China, on a 7-day average. If we presume that Chinese numbers were off by a factor of 100, this still means they were about 8x better than China when adjusted for population. So criteria #1 and #2 were clearly satisfied by China, epidemiologically they were (and still are) doing great. I could expand the graph to cover 2021 as well but the numbers would be even less in favor of the EU.
Then there's the third requirement, namely "reliability of the information". One could try to argue that Chinese numbers are highly inaccurate and cannot be trusted. But luckily there are around 600,000 foreigners living in China, including 70-100 thousand US citizens who are able to rely accurate information on what's happening on the ground. Looking at Youtube, we can find numerous reports of gyms reopening in China all the way back in April, showing that things were stabilizing there. Additionally, widespread infections would result in thousands of reports of foreigners falling sick with the virus in China, but those failed to materialized.
Finally, we can see that other supposedly "zero COVID" nations did not make the cut. Tanzania and Turkmenistan are not there for example, even though both claim to be virus free to this very day. But Rwanda was on the initial list despite being only of minor importance to EU trade, which shows that EU officials did their due diligence and only included countries which were indeed "COVID free" at the time.
This brings us to the last point on "reciprocity" which should be applied on a "case-by-case basis" in theory but in practice was only required from China ever since the list was established. Looking at press releases by EU officials we can see that its a common theme. For example, this statement was made in September 2020:
We made it clear where we stand. Where we agree, and where we disagree. Real differences exist and we won't paper over them. But we are ready to engage. Ready to cooperate where we can, and ready to roll up our sleeves to find concrete solutions. And on those difficult issues, we conveyed a clear and united European message: we want a relationship with China that is based on reciprocity, responsibility, and basic fairness.
This one in July 2020:
After the 8th China-EU High-Level Trade and Economic Dialogue (HED), on Tuesday, EU Commissioner for Trade Phil Hogan said bilateral and trade relations “must be based on the key principles of reciprocity and level-playing field based on clear and predictable rules”.
And this statement was made in April 2019:
Negotiations have been difficult, but ultimately fruitful. We managed to agree a joint statement, which sets the direction for our partnership based on reciprocity. This was our common effort and it is our common success.
So the requirement of reciprocity seems to be merely a reflection of overall EU policy of the past few years. Namely that China-EU relationship should be as "quid pro quo" as possible, in all areas of cooperation. I'm sure EU leaders would love to get similar reciprocity from Japan, US or Israel, but "reciprocity" isn't a current sticking point for those partnerships.