If only one in a million people suffer a reaction to something, then someone somewhere has got to be that one. Therefore if someone you know gets a blood clot after the COVID vaccination, that one case does not invalidate the claim that blood clots are extremely rare after the vaccination.
There are many and varied reasons for people of all ages to have sudden explained blood clots. It does not follow that if someone has a blood clot after the COVID jab, that the COVID jab caused the blood clot, it is merely one of a number of potential causes.
Every day we read about people who suffer all kinds of sudden medical probelems completely out of the blue, that have no obvious cause, and are generally unknown in their age group. Babies and children having strokes. My father, aged 92, died of an infection that generally only children under 10 were susceptible to - I draw absolutely no conclusions from that fact
I wish the Dept of Education would add a good grounding in the statistics of sampling, probability and other basic statistics to the maths syllabus. It would spare us so much nonsense beliefs in science, based on an anecdotal sample of 1.