Thing is, they didn't actually commit to a number. This is the issue. The EU Commission are insisting they did. But the contract is really, really woolly, and all it says is a "best effort".
I feel both parties are at fault but there isn't actually any commitment to a number. There's a commitment to 'try their best' to hit a number. Which, in my book, is absolutely mental for the EU Commission to have agreed to?
Also, there is a clause about taking stocks from 'other EU nations' (I'm paraphrasing) to stock up the EU stocks if needed - clearly meaning the UK. However, the UK is no longer an EU nation, and surely when the contract was signed in August, the EU would have known that the UK would no longer be an EU nation by the time the vaccine roll out began in earnest?