This is in stark contrast to 0.25 million doses AstraZeneca vaccines that were blocked, which is what you are referring to. That has been the only blocked export as of now, at least according to my information.

We may thus indeed have precedent, but it's a very specific precedent which doesn't really serve as an example for a broad vaccine export ban. That's because the legislation on which this precedent was based does only allow such action in the first place if the manufacturer is lacking behind in serving the existing contracts with the EU (a situation in which AstraZeneca is in, but not BioNTech/Pfizer, the top exporter by number of doses in Europe) or if the target of the shipment is a country that is significantly ahead in its domestic vaccination campaign when compared with the EU. This means that there isn't even suitable legislation to instantiate a broad export ban in the EU right now, but just for smaller, more targeted bans; of course this would ultimately not pose an insurmountable hurdle as EU legislation can be changed by the EU itself, but it sends a pretty clear signal that a blanket ban on exports is nothing that's even considered right now.