This is correct.

When we process a block request from user A -> user B, we remove the follow edges between user A -> user B and user B -> user A, and then add a block edge from user A -> user B.

When we process an unblock request from user A -> user B, we remove the block edge from user A -> user B.

I imagine that the "Aleksey checked that he was following me again" was either client caching, or eventual consistency latency. There's no nightly batch job or anything doing that.

Source: I work on the social graph service at Twitter.