Hmm...the EU has exported 50% of its vaccine production.
The UK: 0%
The US: 0% until a few days ago.
The UK: 0%
The US: 0% until a few days ago.
I think your 50% figure is also too high, though it is a high proportion, but these doses are primarily going to wealthy countries.
If the EU were asking for U.K. doses to be routed to other (particularly poorer) countries I would be sympathetic to the position, but this spat is about getting the EU doses, not about equitable access.
Whereas the UK is getting the doses it ordered, at the EU's expense, and has not actually exported any.
So.
Not exactly the same.