Vaccine clots are a different mechanism - they tend to be accompanied by low platelets and are more likely turn up in less common places. If you read this whole article there's a bit of an explanation but essentially not all blood clots are created equally.
"Astrazeneca blood clots: Should you compare vaccine concerns to risks of the contraceptive pill? | The Independent" https://www.independent.co.uk/life-style/health-and-families/astrazeneca-blood-clots-contraceptive-pill-b1834001.html?amp |