It's really not clear at all that the incidence of this type of blood clots is actually higher in the vaccinated. So it seems early to call this a side-effect.

I wish the health agencies were a bit more open about their thought processes. OTOH, the rate of incidence doesn't seem higher than baseline AFAIK, which seems absurd. It also seems absurd that the various health authorities around the world would all make such a big deal of if if there wasn't some elevated risk. So I don't really know what to make of it, but privately, I'm leaning towards the interpretation that the idea is to avoid backlash against the vaccines by being irrationally strict about any potential hazards.