I’m not a doctor, but that’s no blood clot.
You are correct. A blood clot is when blood cells jam up in a restricted area of the circulatory system.
I would think that these clots they are discussing would better be termed as CLOGS.
It is not the piping (veins/arteries) that are swollen/damaged/shrunken causing the problem. It is the growth of some cellular structure that clogs the circulatory system.
What would be interesting would be to see the DNA coding for these artificial structures.