Accidents

They are correlated - more cyclists = less cycling collisions.

And they aren't accidents - accident implies something unavoidable, for which no-one can be blamed. Whereas, at least in my experience, most collisions are wholly avoidable.

Exactly. And another reason to say 'collision' is because the reasons why they occur are quite well-known and somehow 'built into' the traffic environment and actually fairly predictable (much as it would be much better if they were prevented altogether). There is no reason to hide behind the lazy notion of an 'accident' to avoid taking action.