Studies have found that bug count is roughly proportional to program length, across languages. Saying you prefer verbosity essentially means you prefer more bugs. 500 lines is generally less understandable than 40 lines. There may be cases where terseness can be too extreme, but I don't see it here.

Is there some particular aspect of the Clojure code here that you think is overly clever, or hard to understand? This Clojure code uses only one lambda, and in a straightforward way.

I've written a lot of Java, and a moderate amount of Clojure, and if I had to place a wager on which version had fewer bugs, I'd definitely bet on the Clojure. Especially if there were the possibility that it was related to threads.

We could write this in assembly language, and it'd take 50,000 lines, and probably have lots of bugs. The salient point is not (just) the lower line count, but that when code is shorter, that's a good indicator that it's written at a level of abstraction that fits the problem.